If you can find the gorilla! Check out the webkinzinsider site, kinda like the Dis only, it's ALL about Webkinz. Some of the people have posted about buying up 10 of the gorilla if they can find them and then putting them on Ebay to make $$$
OP the reindeer and gorilla are good choices, well any Webkinz is really, I would also suggest getting the pet of the month if you can't find the other 2 suggestions, if the party is this month, the Chihuaha(sp?) is the potm and January is the Yorkie, or so the rumors say. Apparently the potm gets extra special "stuff" when they register it. Good luck, and you are definitely going to be the "cool mom" for that prize!