Can I Help my Bigby's Hand shove a creature off of a ledge?

Question

Situation

Lore Bard, level 10, Magical Secrets choices are Bigby's Hand and Wall of Force.
Known opponents include giants (Frost and Hill). We are in mountainous terrain. I suspect that we'll have some battles where cliffs and ledges factor in tactically, so I am trying to prepare.

What I wish I could do

I have (Lore Bard) expertise in Athletics (+8). I had thought I could apply that to a Bigby's Hand's shove, giving +14, but, after closer study I see that the spell uses the Hand's statistics for the shove. I can't, I believe, apply my expertise to the Hand's shove. (If I can, please explain how that works).

What I'd like to do: lend the Hand a helping hand

Help (Chapter 9, PHB)

You can lend your aid to another creature in the completion of a task. When you take the Help action, the creature you aid gains advantage on the next ability check it makes to perform the task you are helping with, provided that it makes the check before the start of your next turn.

On the second round, since the Hand's shove feature can be activated as a bonus action, I want to use my Action to Help the Hand so that it's shove will have advantage against a Large or Huge creature. The Hand, as written, has advantage on the shove if the creature is Medium or smaller. Help, as an action, provides advantage.

Forceful Hand. The hand attempts to push a creature within 5 feet of it in a direction you choose. Make a check with the hand’s Strength contested by the Strength (Athletics) check of the target. If the target is Medium or smaller, you have advantage on the check. If you succeed, the hand pushes the target up to 5 feet plus a number of feet equal to five times your spellcasting ability modifier {25' in my case}. The hand moves with the target to remain within 5 feet of it.

Does the Hand qualify as someone I can help? That's the crux of the biscuit.

Objective: shove a giant off of a cliff

Round 1 (when cast with my action) Clenched Fist. Punch the Giant for 4d8 Force Damage, or, just shove Giant to keep it away from me. Giants hit hard, and I only have AC of 15.
Round 2 (Hand's shove is a bonus action) Shove giant off of the cliff with my help. It may not slay them, but it takes a giant out of the fight for a few rounds.

Does this work?

I think that it does, but if it doesn't I'd like to know why before I bring this up to my DM. Two embedded concerns that I have are:

1. Can I help the hand? It has statistics, like a creature does (AC, HP, STR and DEX scores) but I am not sure that it can be treated as a creature for a case like this.

2. Do I need to be Large to help with a shove of a huge creature? If so, the Warlock/Sorcerer in the party would need to enlarge me for this. The Shove/Grapple rules indicate that you need to be within one size of the target of the shove. Giant is Huge, Bard is Medium.

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Our other option

Ask the Warlock to cast Hex on that giant with STR as the ability score to hamper, so that the Hand's shove is opposed by a a creature with disadvantage on its roll. I'd like to be self sufficient, but if I can't be that is important to know for our tactical planning.

Answer 1

You can not Help your Bigby's Hand: it is an object, not a creature.

The description of the spell says (emphasisi mine):

[...] The hand is an object that has AC 20 and hit points equal to your hit point maximum. If it drops to 0 hit points, the spell ends. It has a Strength of 26 (+8) and a Dexterity of 10 (+0). The hand doesn't fill its space.

while the Help action states, as you reported (emphasis mine):

You can lend your aid to another creature in the completion of a task. When you take the Help action, the creature you aid gains advantage on the next ability check it makes to perform the task you are helping with, provided that it makes the check before the start of your next turn.

Alternatively, you can aid a friendly creature in attacking a creature within 5 feet of you. You feint, distract the target, or in some other way team up to make your ally's attack more effective. If your ally attacks the target before your next turn, the first attack roll is made with advantage.

The Bibgy's hand hence does not qualify for the Help action.

Answer 2

Use Cutting Words

Beside the matter of the Hand being an object, not a creature, per Eddymage's excellent answer, Cutting Words as an option is a similar but different way to peel this onion. This complement to the Hand's shove costs a resource, unlike Help, and does not involve rolling two dice and choosing the better result.

Cutting Words
When a creature that you can see within 60 feet of you makes an attack roll, an ability check, or a damage roll, you can use your reaction to expend one of your uses of Bardic Inspiration, rolling a Bardic Inspiration die and subtracting the number rolled from the creature’s roll. (PHB, Bard, College of Lore)

The Hand's shove is an opposed ability check.

At your level, Lore Bard 10, a 1d10 is subtracted from the Giant's roll for an average of -5.5 to their roll. The modification to the Giant's die roll will be a value from -10 to -1. This approach has both more risk, and more reward, than Help (if that was applicable - which it isn't).

You can ask your Warlock to cast Hex (per your other option) if are out of Bardic Inspiration(BI) when this situation comes up. Plan ahead: keep a BI or two handy if this tactical situation is looming.

Double down: combine Cutting Words with Hex

If you really need that Giant to fall off of that cliff, combine your Cutting Words with the Warlock's Hex so that the giant has disadvantage and subracts 1d10 from the result.

Thanks to @NautArch for the conversation where this came up.