We took my MIL two years ago. We orginally invited her husband as well, but he couldn't get the time off work.
My mother in law is well into her 60s. She isn't big on consumerism, likes culture, enjoys good food, sleeps late and stays up late, doesn't swim and is slow moving. She has never been anti-Disney, but it never occurred to her she might want to go. She's on a limited budget
We had a four and five year old who move fast, want all the kitchy rides, don't sit well for dinner, get up early. My husband and I spend a lot of money at Disney.
You can see why I was concerned?
We took her sister with us as well. We had planned to pay for two anyway, and this allowed them to break off from us without guilt on our part.
We paid for pretty much everything - hotel (2 bedroom BWV), dinner, food when we were together, and park tickets. They paid for their own souvieiners and food when we weren't together. This allowed us to book restaurants we wanted (and thought she'd enjoy) without worrying about her pocketbook. It let us hand them hoppers with "go where you want" without having to worry about "park days and non-park days." This isn't always do able - we were fortunate to be able to afford to do this this way.
We spent two days running around like mad - goals: Introduce our "rookies" to the layout of the parks, how to take transportation, how to get back to the room. In some ways, traveling with seniors can be like traveling with kids - my mother in law is a bright woman, but she doesn't catch on as fast as she used to. And HAVE FUN! Let the kids enjoy WDW, have my MIL enjoy watching her grandkids enjoy WDW, share some of our favorite things that we weren't sure they'd catch on their own.
Then we split up and met for dinner for the rest of the trip. We'd leave early with the kids, they'd sleep in. We'd ride Goofy's Barnstormer and discover they'd also been in the MK seeing the Hall of Presidents. They poked through the shops in World Showcase, we went to the waterpark.
We spent the last day together, redoing a lot of the Magic Kingdom attractions (or the stuff we'd missed).
Turned out to be a great trip. Next year we are taking my parents on a
Disney cruise - and I'm not sure about that - my Dad gets crankier and more set in his ways each year.