Depending on how old is the toddler? Like for my son, he is 2 so basically he can eat anything, can prepare small cut fruits, snacks like biscuits or cakes for them, cocoa puffs, mini sausages,mini buns etc
After they leave, normally will vaccum and mop the floor....
With small toddlers, firstly i will try to move small breakable stuff that are within reach, into a room and keep it closed.
Foodwise, I will ask the parents if there are any food restrictions before hand cos some children have allergies to some common food like wheat, peanut, egg, etc. Some parents also don't like their children to partake sweet stuff and fast foods like hotdogs, nuggets, etc. Usually, we will do a potluck with fruit juices, fruits, homemade sandwiches and snacks like muffins, cookies, etc.
Re cleaning up, depends on where they are confined to. For extreme cases, I had to change the bedsheets in the bedrooms cos they ran in and played on the beds while eating. From that time on, I learnt to place restrictions on which areas are out of bound. If just in living hall, I will vaccum, mop and wipe all surfaces they can reach.