Ah. I sometimes have a small child (I think he is 2ish - still in diapers but can run around and talk some) brought over to me for babysitting for an afternoon every few months- I just never thought to do all the prep you are doing. I don't have children so I don't know all the disasters that can occur and so far he is still intact. I do watch him closely with the dogs and put them out when they seem stressed. But he has a dog, so he usually is not too awful with them. The cats fascinate him, but they can escape him easily enough. Perhaps his parents are suspect for leaving him with me. I also am usually alone with him, so I don't have other small children around that I have to be concerned about. I find at the end I am sore from wrestling around with him on the floor or from picking him up and letting him ride around on my shoulders or back which he seems to enjoy (he runs at me and tries to climb up me like a tree to get to my shoulders).
I hope it goes well for you.