Intriguing question (no, really, it is). To keep the balls warm en route (though it is a pretty short route), you might consider inserting one of those microwaveable warming stones that The Wife and I use for big baskets of fresh tortillas (mic stone, place in bottom of basket and cover with towel; contents stay warm).
Or, you could just put the balls in the oven for a few minutes when you get there: that way, you could warm them and dry off any potential moisture that might have accumulated.
"Don't you ever underestimate the power of a female." Bootsy Collins