We have booked two houses for long weekends during the summer. A change of scenery and some time hiking and in the river will be gratefully appreciated.
We do have a schedule for DS. He does some type of academic thing in the morning, duolingo, Khan, workbook, starting at 9. He plays from 9:45-10:30. He does something academic at 10:30, normally reading. Plays at 11:00, although he has been choosing to keep reading. Lunch around 12:00. DH and he do something from 1-3. I do stuff with him from 4-5 and then make dinner. Family walk.
But we have 1 child who is pretty chill.
There is no reason why your husband isn't doing more. If he is checking out of the kid stuff then gets all the laundry, cooking (breakfast, lunch and dinner), and cleaning.
I would look into hiring a high school kid to come and do stuff with your older kids during the afternoon. My DH would not, he is more risk averse then I am.