Spring rolls wrapped in either rice or vegetable wrappers (veggie wrappers could be thinly sliced zucchini or daikon, lightly steamed cabbage or chard, Romaine or Boston lettuce ... )

Hummus with gluten-free crackers (homemade or storebought)

If they eat meat, seafood and/or dairy your options are just about unlimited ...

Deviled eggs

Any toothpicky meat/fish/shrimp/sausage thing

Cheese cubes with quince paste and/or or a selection of fancy honey

...