I'd probably have to plan as much for the kids as for the DH. Is he coming in the middle of the trip or some such scenario, and that's why you're planning for him rather than for family?
What sorts of things does he like to do? Is he a thrill ride guy? (Splash, Space Mt., RnR coaster, ToT!) Would he enjoy something like the Richard Petty Driving Experience or Parasailing?
In 4 days you should be able to show him the highlights of each park, so it will help to know more about his likes and dislikes. I take it a golf day or a day at a water park is out, since he'll want to use his 4 Day Hopper. Without more info, I'd say don't miss Illuminations, Fantasmic, and the MK fireworks if they're showing while you're there. Other than that, you'll really be able to see the major attractions in 4 day's time.