I think a non suspended fat bike could be ideal for you, the big tires do a lot to smooth out the ride and rolling resistance is much better than you would expect.

If you end up with suspension, Rock Shox has what is called "bottomless tokens" for a number of their forks (bluto included) and it would be worth using as many as the fork can take. In short they will reduce the volume on the air spring causing the air spring to become stiffer quicker as you go through your travel.