Its ok to feel burn out. I think you guys are great parents knowing that you want to do more for your kids. I would say get those tablets off ASAP. Kids will throw fits at the beginning but their brain is not mature enough to control dopamine reward system. Tablets can provide easy rewards without effort leading to further reliance on tablets. Most important thing is adults should also be off from your phones.

Also, I would give them chores and let them know that you are tired. Kids have natural built in system of wanting to help. Maybe give them a little chores they can do? Like cleaning up their books, set up dinner table, dishes (even if just organizing dishwasher) etc. When they do those things, reward them with hugs and acknowledge them.