I agree with 5 Little Monkeys and Crayola. When I had younger (10 months old) kids in my daycare they had 2 naps per day - one at 9 (the children arrive at 7:30) and one at 12:30/1:00ish. I used the time during the morning nap to do a craft (or playdough, or baking, etc) with the older kids. I would let them sleep until about 10-10:30, give them a snack and go outside after that (weather permitting). Maybe you can start heading in that direction so that by 9 months or so they can follow that schedule. Another option might be to get a stroller that can accommodate everyone and start taking a daily walk during one of their naptimes so the older kids (and you) can get out?