Outside play is the end of the day. That is the only time everyone was up and fed and ready to play. Try adjusting the two that sleep from 10:30 to 12:30 by putting them down at 10 and getting them up at 11:30. Then lunch and naps in the afternoon can start staggered but all end at 3ish then snack and outside from 3:30-4:30. In nice weather I put the older ones outside for snack and stand at the door which is off my kitchen and the little ones still eat in their high chairs but at least the older ones get an extra 10 minutes of fresh air.

10-10:30 would be an activity for the older kids by putting the second group of 1 year olds down before getting the first set up so having a half hour of overlap still is enough time for a story and craft. The one year olds don't need much for programming till they over the morning nap routine anyways. Rather than push the one to move nap later I would be pushing the other two earlier for a bit and then gradually move lunch to 11 and they go to sleep for 11:30 - 2:30 and older kids have lesson time from 12:30-1:00 with the first one year old watching.

Consider a play yard area for the one year olds they go in if awake and that leaves you to be with the older kids for periods and then on their own for periods such as introduce an game and then leave them to play.

Schedule in mixed age groups is always the hard part. Serving lunch in two segments since both groups may be eating different anyways is also an option - feed the little ones in their high chairs eating finger foods while you do story and craft at the table with the older kids and then give them lunch to eat while you start naps for the babies. Lots of experimenting and as soon as you figure it out they will have moved on to a new schedule so it is never ending.