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What is your party facing for foes?

For your encounter in question:

The stock Drow indeed have light sensitivity -- so spells and effects based on bright light are more useful than the norm; this may affect your choices when it comes to cantrips. Also, sleep is the only effect 5e elves are immune to; they do have advantage on saves against other charm effects though, so keep that in mind. Finally, you may wish some means of piercing magical darkness -- all drow get innate 1/day darkness and fairie fire, which can be used by them to negate at least some means of generating light without hindering their own combat effectiveness.

A build-specific note, before we move on

Note that "save or X" spells don't work with Spell Sniper, as the feat specifies that it only affects spells that make an attack roll against the target.

For the general case: What is your party facing for foes?

Their criticism of shield is off-base as well; it is actually one of the most powerful defensive spells available to an armor-less mage of any sort, because its +5 AC bonus stacks on top of both your DEX modifier and base AC from other sources (such as mage armor and barkskin) and is available as a reaction against someone attacking you.

Their criticism of shield is off-base as well; it is actually one of the most powerful defensive spells available to an armor-less mage of any sort, because its +5 AC bonus stacks on top of both your DEX modifier and base AC from other sources (such as mage armor, your Draconic Ancestry, and barkskin) and is available as a reaction against someone attacking you. In other words, you have 18+DEX AC available to you whenever you are attacked, despite wearing no armor whatsoever.

Future spell suggestions

While your theme (ambush back-line leadership with charm spells to disrupt the order of battle) isn't at all bad (save for Spell Sniper not working with save-or-X spells), you may wish to augment it with more combat-useful charm effects and complementary spells. My suggestions for this theme (going from second to sixth level spells) would be:

• Crown of Madness -- very useful for disrupting battle order, and at a good distance too
• Detect Thoughts -- get inside your enemy's head
• Invisibility & Misty Step -- you'll need some help skulking around to get in range for your save-or-X spells, so take it
• Counterspell -- shield's counterpart for going up against higher level casters
• Fear -- AoE crowd control, mind-affecting-style
• Gaseous Form -- more sneaking assistance
• Hypnotic Pattern -- medium-range AoE charm/crowd-control
• Greater Invisibility -- cast your spells while invisible
• Dominate Beast -- be the bane of the dogs of war
• Confusion -- throw entire war parties into disarray
• Dimension Door -- your first outright teleportation ability
• Dominate Person -- obvious choice
• Mass Suggestion -- again, obvious

• Sentient humanoids in small quantities (whether it be a orc/goblinoid, cultist, bandit, or more exotic theme) -- these encounters play straight into your hands with charm and suggestion, especially if you can identify and target leadership figures within the NPC ranks, and doubly so if you are facing NPCs with poor mental (usually Wisdom) saving throws.
• Swarming humanoids (goblins, kobolds) -- again, identify and target leadership figures. Being able to charm the goblin war chief into making an entire company o' goblins bow to your feet beats the pants off fireballing them and then having to spend several rounds mopping up. Bonus points if you can convince the war chief and his company to fight alongside your party for a while!
• Predatory animals (wolves, bears, etal) and monstrous predators (owlbear, anyone?) -- unfortunately, you are now in Druid territory; Sorcerer mind-affecting spells are designed to attack humanoid foes for the most part. (Sleep is vastly underpowered in 5e as it works on a hit point basis.) Thus, you're stuck with direct damage as your only remaining option...thank gosh for damage-dealing cantrips!
• Mindless undead -- this is the realm of turning Clerics, as most low-level undead don't have the brains to understand your charm person and suggestion attempts. Again, you'll need your damage cantrips here.
• Fiends -- these are flatly, a pain in the rump, even if you are dealing with their weaker forms. They have nasty damage resistances and magic resistance -- very few things can deal with them well (fey knight paladins get the turn the faithless class ability which helps, but that's about it). So, I wouldn't worry about your effectiveness against them.

• Sentient humanoids in small quantities (whether it be a orc/goblinoid, cultist, bandit, or more exotic theme) -- these encounters play straight into your hands with charm and suggestion, especially if you can identify and target leadership figures within the NPC ranks, and doubly so if you are facing NPCs with poor mental (usually Wisdom) saving throws.
• Swarming humanoids (goblins, kobolds) -- again, identify and target leadership figures. Being able to charm the goblin war chief into making an entire company o' goblins bow to your feet beats the pants off fireballing them and then having to spend several rounds mopping up. Bonus points if you can convince the war chief and his company to fight alongside your party for a while!
• If you are dealing with a leader-less swarm of humanoids, you still can sow considerable confusion within the NPC ranks with well-played charm or suggestion spells.
• Swarming monsters (stirges, etal) -- this is bad news for you, and where AoE crowd control (one of the normal mage specialties) is most needed. Hopefully, your DM's Inspiration is a recognition that you're playing a character that fits well with his future plans, and not simply "this character is underpowered, so it must be good RP"
• Predatory animals (wolves, bears, etal) and monstrous predators (owlbear, anyone?) -- unfortunately, you are now in Druid territory; Sorcerer mind-affecting spells are designed to attack humanoid foes for the most part. (Sleep is vastly underpowered in 5e as it works on a hit point basis.) Thus, you're stuck with direct damage as your only remaining option...thank gosh for damage-dealing cantrips!
• Mindless undead -- this is the realm of turning Clerics, as most low-level undead don't have the brains to understand your charm person and suggestion attempts. Again, you'll need your damage cantrips here.
• Fiends -- these are flatly, a pain in the rump, even if you are dealing with their weaker forms. They have nasty damage resistances and magic resistance -- very few things can deal with them well (fey knight paladins get the turn the faithless class ability which helps, but that's about it). So, I wouldn't worry about your effectiveness against them.