Plan #1 - Take the TV remote and place it somewhere on the MUP. When he asks, tell him where it is and that he should go get it. Every day place it 20 yards farther away.

Plan #2 - Go to Home Depot and pick up a bunch of those paint chip sample things. Tell him you want to spend the day talking about his feelings on these paint chips match different items in the house. This is how most guys got started riding.

Plan #3 - Buy a smaller size of every article of clothing he has, switch out the closet and drawers one day.

Plan #4 - Some how, arrange to break his tail bone. He won't be able to sit in a regular chair or car seat for about a year. Inflatable donuts won't help because the weight of the internal organs. The only way he'll be able to sit down for more than five minutes is to get on a bicycle seat. This technique worked on me.