So I'm a stay at home dad for the time being while I'm waiting for a work permit, the thing is when you take care of kids from the morning till night it becomes physically and mentally draining because you're not mentally challenging yourself and always running around picking up after them. I just want to say that despite it being hard, I love my kids but everyone needs a break. That small amount of time that you and your wife can get together could mean the world to her and is important to maintain a good relationship. If the relationship is good and solid, the children will be a lot happier to see their parents happy making the job of the parents a lot easier in most situations since they'd be less stressed aswell.

Perhaps look into a daycare or nanny that can watch your kids for a few hours once or twice a week allowing your wife to recharge her batteries. Remember, if your wife is stressed out it'll reflect onto the kids too. A daycare is always a solid choice since kids can interact with others and learn to be social before pre school thus making integration into school easier.