Re: Do you think this is an impossible schedule for DH?
I know I am the lone voice here, but I think it can work. There are essentially only 2 blocks of time when baby would need to sleep during the day - between when you leave in the morning until DS wakes up, and from the time he gets home from dropping DS off to the time he leaves to pick DS up. Basically, you would need the baby to sleep from 7:15 (gives you time to get baby to sleep before leaving the house) until 9 or 10, and then again from noon-2:30. This shouldn't be a huge deal, honestly, especially the noon-2:30 time (give DH a chance to nap, in addition to the 4-5 hours he would get in the morning). We did 2 years of half-day pre-k/kindy and we live 1300 feet from the school, but the sidewalks are not passable in the winter. DS2 would fall asleep as soon as we left the driveway to drop off DS1, and woke when we got home after picking him up. In the months of nicer weather, I would walk him and DS2 would fall asleep in the stroller, so when I got home I would just park the stroller inside the door and he would wake up on our way back to the school 2 1/2 hours later. With a new baby, and the convenience of an infant carrier - piece of cake.
If he didn't already have this schedule and be accustomed to it, and if he didn't usually sleep for just 5 hours, I would probably think differently. But, given those factors, and the specific times of your DS' kindy - I say it is doable, totally.