I might recommend some foods that you can eat standing up with only one hand... Maybe some sort of protein based wrap.
And a vegetable skewer

Grill some steak with fajita spice ahead of time
Grill some Portabella Mushrooms ahead of time
Saute and Caramelize some onions ahead of time
Make a garlic or chipotle pepper Mayonnaise

Put it all together in a wrap/ cut in half and you are ready to go when your crew is ready to go

Greek Salad Skewers

on a 10" skewer

alternate
grape tomatoes
feta cheese
plum tomato quarters
artichoke hearts
cucumber slices
Red onion slices

Marinate in greek dressing ahead of time[b][/b]