I have almost 4 year old twins. We do use the TV as a babysitter often because I am gone 11-12 hrs a day Mon-Fri and wife needs to clean and make dinner. On weekends they get it as I get things done around the house like yard work and house fixing. They are not old enough to help. We are having some money issues and TV + internet is $200 month. Could cut to about $75 for just internet and DirectTV now.
I have to disagree with the "not old enough to help." 4-6 year olds are the BEST time to teach them to help. They are soooo excited to be with dad, they will hold things and hand screw drivers. My then 5-yo pulled frozen chicken breasts out of the freezer, added some broth, covered the pan, and put it in the toaster oven the day her little brother was born. My husband made the rest of dinner but she did that so it could cook for a few hours.
You have REALLY got to get your wife on board with this. If she is not, she will be using the tv for the kids behind your back, even if she agreed not to. And that will cause marital problems. My kids have never had tv as a babysitter, even when small. They built with blocks, did puzzles, build with wooden train tracks, etc.
When they learned to read, that is ALL they do (I have seriously weird kids - they read all the time and fight over whose turn it is to play the piano

They can clean up their own messes, unload dishes from the dishwasher, sort laundry, wash sinks and mirrors. There are a dozen lists with age appropriate chores for children. Your wife should not be doing everything. Although, she will feel that it would be faster and easier to do it herself. She has to change her mindset (and you too "like yard work and house fixing") that you are not doing the things to get them done quickly, but to teach the kids how to do them. That will free some of her time AND occupy the kids instead of watching tv.