Well, I've always told people if you can get to the heart of why and in what ways people "don't care for WDW" (or DL), then you can more effectively increase their enjoyment and tollerance.
For example, is it the crowds? Money? Frantic schedule? No time away from the kids EVER? No personal time? Different sleeping schedule? Chaos? Amusement park food?
All of those are things I can think of. I'm sure there's a ton more. With each one of those, you can work around it. If she's a morning person, but you aren't, have her enjoy herself in the am doing something just for her and then you get the kids up and ready and meet her somewhere. If she's a night owl, but hates mornings, on a few mornings, get the kids ready, out the door and let her sleep in. If it's privacy, spring on a suite, or rent DVC points, or rent a home off site. If it's no time away from the kids, either encourage her to spend some time alone doing whatever (for me it would be sitting by the pool with a beverage and book!), bring someone with you (babysitting, aunt, granparent) who can take the kids for a period of time for the two of you to go somewhere, or use some of the various babysitting services. You can do that before the kids are 4. If it's the frentic pace, see if you can plan a more leisurely trip. Either adding days, or not do the "must see everything" kind of trip. If she simply maxes out on the mouse, maybe look at going to Sea World or Universal. Or maybe she could take the older kids and go while you go to fantasyland with the youngest. Or maybe devote one night to a nice dinner somewhere off site or in DtD where everyone gets to get dressed up nice and go out.
If it's money, see how you can get the best bang for the buck, and show her the savings you find. Between now and your trip, give the kids Disney gift cards or Disney dollars so they have spending money on the trip. We're also purchasing alot of the "extras" that really add up as x-mas presents. They are getting pins, pens for autographs, fanny packs, light spinners, I even got Disney beach towels for like $1.99 at Disneyshopping when it all went on sale and I had a discount code. For DD, I got bathing suits, too. It's a present, and it will be useful on the trip. Cuts down on what I might spend on the trip, and will reduce the "I wants" on the trip.
As far as "adult" things to do on a trip, there's a ton. My DH would love the Richard Petty experience, and I would really enjoy that as well. There are a number of walking tours (I'd post on Theme park strategies for some good ones) that focus on the art of Disney or the world renowned landscaping/horticulture. There are behind the scenes tours. There are cooking symposiums/classes. There's just a ton of non-theme-park riding ideas. You can rent a car for just a day right on property, if she wanted to go to the outlet malls and do a bit of shopping.
I've had similar experiences with my DstepMom and DH. DH gets kinda weirded out about the cost of the whole thing. DstepMom doesn't like rides, doesn't like crowds. When we went to WDW last time, we had character time when they could take tons of pictures of the kids, by going on a non-park day to Chef Mickey's, and then going to DtD during the day to shop and wander around. We spent one day at EPCOT, pretty much together the entire day, and she really enjoyed that. Then, on another day, we went to AK right when it opened, went on the safari (which is really all she was interested in) and then went over to MK where they spent a bit of time on a couple of rides (like small world and Daddy went with the boys on autotopia), and then they went off on their own and we spent the rest of the day doing MK. It's different than I would do it, but worked well for us.
