Ahh I see. I was trying to figure out how 3 meals/snacks would fit into 4 hours lol. IMO, you need to space it out a bit more. If they are only there for 4 hours they don't need to be eating right at drop off and than every two hours after that. They are 3 and 4 so they old enough to wait until snack IMO. I would feed them twice and thats it, especially depending on how much you are getting paid.

You will need to set boundaries with the parents as well as the children. Since they are the only family you look after, I would definitely set up a schedule. If it's 9-3 or whatever, this allows you to plan your day with your own children for when you are done work. It would be nice to know if you had time to run to the store before they got there or whatever it may be. I wouldn't want to just be sitting at home waiting for them to show up and than wondering when my day was over.

Good luck!!