Damnbamboo...
I chatted up a chap who ran the reptile dept at our local zoo. I hired a hall, and we had 3 crocs, (on leads!) pythons, armadillos, tree frogs, scorpions, chameleons, iguanas, hissing cockroaches, and a bird of prey. It was brill. He has since started his own company I believe, if you want message me and I'll hunt out the details.
He was 4, the theme was dinosaurs, I got them all an Indiana Jones hat to decorate when they arrived. Dog tags with their name, and rank (explorer etc) on. Bought 9ft cardboard cut out T Rexs. Chatted up the local army lads and got them to cover the entire inside of the building with their camouflage nets...we lost a tree frog escapee in there for 20 minutes, that was fun :) I got helium balloons in the shape of pterodactyls. A bouncy castle in camouflage colours. A facepainter who gave them all triceratops horns on the way in. A balloon modeller who made them all balloon dinosaurs whilst the zoo was setting up.
So after all that, they can go fuck 'emselves if they want a bag of tat to go with their hats, dog tags, balloon model, helium balloon and piece of cake :) The Indiana Jones hats, dog tags, face painter and balloon modeller came to under £150. And were superb. I would have spent more than that on tat bags for the 45 guests.