Entree:

Popcorn
Rice crackers (Sakada/home brand) with cheese and ham
Most plain chips are gluten free, but check the seasoning doesn't contain gluten.

Mains:

Some frankfurts are gluten free (check the packet, I *think* it's the Don ones you buy in packets in the deli aisle)
I cut up chicken thighs into strips, roll in gluten free breadcrumbs (don't bother with flour/egg as the fat on the thighs makes the breadcrumbs stick), spray with cooking spray and bake in the oven for about 15 mins - "chicken nuggets/strips"
Home made chips or oven baked roast potatoes
Fried rice with veggies, chicken/ham/bacon- cheap and easy and most kids eat it. Tamari is gluten-free soy sauce

If you put the above things in the middle of the table with tongs, most kids have an awesome time serving themselves.

Dessert:

Fruit platters - on skewers is great fun (think "fairy wands")
Lollies (check packet)
Chocolate (check packet)
Target sell gluten free Cheezels in party packs of 10 - you could just give each party child their own packet so they don't get cross-contaminated

Cake mixes can be gluten free - I'd get the freedom ones as they don't taste quite as bad.

Hope this helps.

ETA: It would be easier just to do the whole thing gluten free - that way no kids "miss out".