Actually, people in the handicapped section DO get in before everyone else and can pick their viewing spot. In November 2011 (and I believe well before then as well) they had a separate waiting area for handicapped viewers, right at the front. You do need a Fastpass to view the show (free one is best; you might want Yellow or Red?). But the handicapped queue people are let in first, before the regular queue behind them. They can then choose either the handicapped section or anywhere else in the viewing area.
If multiple shows are offered during your trip, I'd either make sure to go to the early show (which will involve substantially more waiting, as I hear they start loading people into the viewing area an hour prior to the show and you'd have to be there before then) or stay out of the area until the first show is over. I THINK you can probably show up to the second show shortly after the first one ends, meaning you could in theory hang out somewhere away from the first show and then when that's over, head over to the back of the handicapped viewing queue, which will still get you in before anyone else. I can't guarantee that though, so if you don't have 2 nights to potentially devote to World of Color (in case the late show thing doesn't work) you may just want to go to the first show.
(In normal circumstances, I'm not certain I think it's worth the trouble to see the first show, even though it's nicer because you don't get at all spoiled for the show. In your husband's case, though, I think a lot of the appeal of the show would be the music, which is hard to avoid if you're in the area.)
Alternately, if you yourself aren't that interested in the show (or don't think it's worth the hassle), you might just view it from an alternate viewing area in the back--some of those get pretty close to the fountains, and my GUESS is that your husband wouldn't be able to see the projections anyway (they're not that clear, though I heard a rumor they're getting new projectors at some point which will help with that).
Low season crowds may or may not help you--World of Color is a "ticketed" event so I believe the first show pretty much always "sells out" which makes the crowds for the first show, at least, pretty similar regardless of season. But if the handicapped viewing entrance continues to work like it did in November (and I don't see why it wouldn't) you should have no trouble getting as close as you like.
Have a great trip!