Agree with the others. A rest time for non nappers is needed. I once had a mom ask if her daughter could not nap anymore and I said yes as she was getting older (3.5). At first I just brought her upstairs with me and she watched tv, did puzzles, coloured, read books and I ate my lunch and than took some time to go online or just do whatever. However, shortly after I incorporated a mandatory rest period of 30 minutes. She would lay on a cot downstairs for that time while I came upstairs and ate. Than I would go and get her (if she hadn't fallen asleep) and she would come upstairs to do the quiet activities while I still enjoyed my break.

We don't get set breaks unless all the kids are down at the same time. I don't think a 2.5 hour kid free break is needed (but it is nice!!) and I don't think it would be easy to contain an awake child for that long so that is why I went with 30 minutes. Pick a length of time that suits you and tell the parents that they will be resting during this time so that you can get a break as well. Good luck!!