I agree with GreySage's answer, but as I'm currently playing through LMoP myself, with a group of entirely new players, I wanted to add a bit of extra insight based on my own experiences of this module specifically.
If this doesn't help you, then hopefully it might help others with similar questions, especially if they're DMing for new players. Potential spoilers follow:
Adding more money to treasure hauls will not unbalance this game.
This is primarily for the reason that GreySage stated, particularly in this module 'money is basically useless'. While this treasure hoard may seem small, when they arrive in Phandalin, they have the potential to also get:
- 50 gold from the Lionshield Coster (for reporting the location of their lost supplies)
- 50 gold from Sildar Hallwinter (for escorting him to Phandalin)
- 10 gold each from Barthen's Provisions (for escorting Gundren's supplies)
And, the adventure's generosity doesn't stop there. Your PCs will soon be rolling in more money than they have any use for.
The module does attempt to 'solve' this issue by presenting the players with a potential 'money sink', later, but as most games end soon after, the money is still largely useless. That's unless you decide to keep playing, with these characters, in this world, after the published adventure is complete, in which case, this question about the cost of renovating Tresendar Manor, may be useful to you.
Be wary of removing the health potions
If you're playing using the LMoP pre-generated characters then you'll only have one healer in the party. If they go down, the PCs having a few healing potions handy is invaluable.
Health potions will also help to keep the game moving when it might otherwise grind to a halt. Tresendar Manor, likely the place they'll head next, has potentially 7 combat encounters, some of which could be fairly challenging. So, if you want to maintain some realism, and avoid you party 'short-resting' (or trying to) at every available opportunity, in the middle of enemy strongholds, then keeping a few healing potions could be the solution.
If you want to add an extra item, consider making it a teachable moment
This may not be relevant to your situation, but I'm including it here, just in case it helps you, or anyone else with a similar question later. If you want to roll for magic items then I agree with everything GreySage said.
My players were all completely new to DnD so I wanted to use this first dungeon to teach them a lot of the rules, as we went. For example, the Goblin Ambush was the first time I taught them about turn order and action economy. In this treasure hoard I wanted to teach them about the potential value to be gained from beating the 'boss' and also, mechanically, how the item attunement system worked.
I therefore chose to insert a completely homebrewed item into this hoard (without changing it otherwise). It was something like this:
Fang of the Packleader Wondrous item, uncommon (requires attunement)
This vicious-looking canine tooth must have come from an impressively large wolf. It has had a hole drilled through it and been threaded onto an old ratty piece of string, creating a crude pendant.
Once attuned, this item grants the bearer +1 on all Animal Handling checks and Advantage on Animal Handing and Intimidation checks that relate specifically to Wolves.
Now, whether this item is balanced or not (it was my first attempt at homebrewing anything), is not important here. I wanted it to be something that would thematically fit as being owned by Klarg (who is rather attached to his pet wolf), so that they could find it actually on him, rather than just lying with the other stuff in his hoard.
Including the 'Fang of the Packleader' allowed me to explain how attunement worked, stoke excitement for future treasure, and provide a reward that was slightly more interesting than simple money and health potions. Limiting its usefulness also meant that it wouldn't be gamebreaking. If you don't want to risk homebrewing something for your own game, consider using one of the 'Common Magic Items' from XGTE.
I also wanted to show my players how items that they found could be good plot-hooks for roleplay, character growth, and narrative. So, after a few long rests, I started seeding the idea that the bearer's own canine teeth were lengthening, and that their eyes were slowly turning gold, as they become more wolf-like themselves.
The PCs increasingly more wolf-like appearance provided some fun opportunities for inter- and extra-party roleplay as the campaign went on. Ultimately, later in the campaign, to reward the pleyer for leaning into the changes in his play, once most of the rest of the party had found significantly more useful items, I had the item 'evolve' to provide its bearer 3 uses per long rest of the Wolf's ability 'Pack Tactics'.
Anyway, have fun playing the Lost Mines of Phandelver. Whether you choose to use any of this, or not.