Funny you’re asking for ideas. I was just thinking about bounce back plans for 2020 and am considering a four night trip just DH and me for a belated 20 years together celebration. Haven’t given much thought to how to surprise him with it yet.
As for things to do. Are you planning to branch off with your mom at all or stay together with the larger group? If branching off, I’d suggest reservations for Candlelight Processional (lunch preferably as it’s typically a bit cheaper). I wouldn’t take a 2yo to CP but it’s great for older kids and adults. If your child won’t be up for the nighttime fireworks, maybe a dessert party.
Other options are the Highway in the Sky Dine Around, Savor the Savanna: Evening Safari Experience, or one of the tours.
A very low cost (possibly no cost) option is simply to resort hop one day and take in all the Christmas decor. Especially easy to do a monorail loop.
I don’t know about MVMCP. We did it last year and had a mixed opinion.We all loved the parade (early) and the lower lines for rides. My older son and I stayed and concentrated on rides. DH and my younger son had had enough after the parade so they bailed and went home. I would have been annoyed to spend all that money for such a limited experience but it was included with our package.
We used a scavenger hunt to surprise our kids last year - I could see doing an adult one. My cousin had her kids open a box filled with a giant Mickey balloon (and regular balloons) for their reveal. Maybe have her open a letter from Mickey that says he’s going to see her real soon?
I may just keep it real simple and buy him a new magic band along with a card that says “We’re going ‘golfing’.” Friends of ours just did a trip without their kids and told the kids they were going on a golf trip.