Thanks to all the awesome GTers who provided excellent advice for my babysitting adventure. The kids LOVED Shiny's baking soda treasure rocks aka "magic dinosaur eggs". We spent a lot of time dancing and watching old Mickey Mouse and Silly Symphony cartoons, and we went swimming, had craft time and then pizza for lunch AND dinner (as per instructions from parents). There was only one mini-meltdown related to a skipped nap and the perils of toothbrushing, and a four year old's desperate efforts to avoid bedtime. Miles the wonderdog (who is exhausted today) was a DREAM with these children, playing hilarious lifeguard around the pool and was content to snuggle belly-up when the kids wanted to watch TV.
All in all, a great success! I appreciate everyone's suggestions!