You can try to do the mule ride, but I will tell you that those are usually sold out up to a year in advance! The South Rim is probably your best bet since it is set up better for visitors - the North Rim is quite a drive around, tho they do have a horse ride to the bottom (weight limits and pricey) where you stay overnite, but seemed to be set for hiking.
There are places to eat there - couldn't tell you anything about pricing as it's been a bit since we were there. However, keep an eye out as you might well see a California condor there (one flew right by the window where we sat!) - seems the birds like the area (this was the south rim side).
There is also the Indian side of the Canyon - you can rent horses to ride down to the Havasupai area (see the falls!) or even copter in if the weather permits. However, this might not work for you w/your husband's MS - it's 12 miles and might be too much and you'd have to camp out for the most part until the horses go back up next morning. (don't know about copter tho - check w/AAA if you have it)
Williams, AZ isn't too bad (or wasn't) - small town that had a few places to stay and eat - nothing fancy tho! Not too far from the Canyon either.