As others have said, I think that they will love BCV. I own at BWV and love the boat launches and the very wide sidewalks that circle the lake from Epcot and DHS and to BWV, BCV and Swan and Dolphin. And they can take the bus to AK and MK.
I don't know if this will help, but I will tell you my experiences over the years.
When I first starting using a cane to walk everywhere, I didn't have a problem. Then slowly over the years, I would stop and sit on a bench at MK for a minute or two and continue on. Then over the years there were more frequent stops to sit on a bench and people watch and then continuing on my trek through the parks.
Then I found it difficult to get from my resort room to the bus, etc..
And over the years they removed all of the benches from almost everywhere around the MK center square and up and down the sidewalks. There used to be benches in a lot of places in MK and other parks and everywhere else. I surmise that as MK got more crowded they removed the benches so that the sidewalks would not be as crowded.
That's when I rented a
scooter at MK, and it was great except of the issues with of using the scooter among walking people.
But, I still had a problem getting from the bus to my resort room and visa versa.
So I rented a scooter from an outside source, and I used it everywhere. Such freedom to go and explore other resorts and out of the way places.
Then next year I bought my own three wheel portable scooter that I take with me to WDW. I have been doing that ever since.
Now, even with the scooter, and the older I have gotten' I don't spend as much time each day in the parks because of medical reasons.
But I still enjoy WDW and just go at a much slower pace until I get that feeling. I might even do an every other day thing where I would go to a park for half of a day, and then stay at a resort every other day.
It sounds like your parents have great genes, and they are much healthier and stronger than me.
Just keep an eye on them, and try to determine their pace. Let them people watch, enjoy the shows and what rides that they want. But even though they may be smiling, they may be tired and slowing down or even in pain.
Even though I may make a great schedule to follow in the parks, I have been just going with the flow and cancelling reservations in the allotted time if I can.
Good luck.
Ray