you could offer rice crackers, radish and cucumber slices for topping with dips, chickpea salad, etc.
does Bob's Red Mill make a gluten-free bread mix you can try out for sammies?
also, Allyson's butterscotch amaretti cookies
are ridiculously good and super easy to make and don't require a million flours (just almond meal)!
if your gluten-free guests are okay with gluten-free oats you can purchase some and make susan v.'s blueberry oat bars
. i've had tasty successes with them many times and you can switch out the fruit, too!