Like Jeff mentioned, not a lot closes for lightning. But because so much of DLR is outside it does very much depend on how rainy it is (and therefore how wet are the ride vehicles/tracks are) if they then move to close them.
The list he linked too is great. I will add to that list that if it’s the rare storm that brings a lot more water than the parks are used to dealing with some additional ones that will get too waterlogged to continue loading guests because of a risk of slipping: Astro Orbiters, Dumbo, Casey Jr.
In DCA with so many rides being out in the open in the Pixar Pier and Paradise Garden areas the lines for Toy Story (half inside) and Little Mermaid will balloon when it’s raining. And there will be the most closures in that area, so that is the only area that I would potentially avoid. But Carsland might also be tough since Racers sometimes is impacted (usually only with lightning, but there are times when its rain) and always Luigi’s is offline as the ground has to be dry for the trackless vehicles to work.
I think the biggest challenge in DL is finding a place with a seat & under cover to ride out the rain so I find it very helpful to have ADRs especially since they tend to give the ADRs the priority (if they can) to the ADR’s to sit inside. But some places (Cafe Orleans, Carnation Cafe & River Belle Terrace) only have so much seating inside so those aren’t guarantees at all. QS places with indoor seats or good cover will become jammed. The ones in DL that are inside: Golden Horseshoe, Red Rose Tavern, the indoor portion of Alien Pizza Planet, a small portion of Plaza Inn, and then like 5 small tables in DL’s Starbucks (Market Cafe). Then good covered but still outdoor seating will include Hungry Bear Cafe, Ranco del Zocalo, and parts of Galactic Grill and possibly some of the patio seating outside Alien Pizza Planet (the part that borders where the walkway into the Spact Mtn ride entrance).
In DL the indoor places will be: Starbucks (Fidler Fifer Practical, but a lot of these booths get filled and stay filled by the same party the whole time the rain passes, it’s the go-to spot for rainy day hanging out), a portion of Smokejumpers tables, a portion of Flo’s Cafe tables. Then there are a lot more covered tables in DCA between the Paradise Gardens area especially and also in Hollywood land nex to Philharmagic.
One place they close in heavy rain to avoid tracking water onto the carpets is Mr. Lincoln’s and that might include the lobby area and DL exhibits in there. If it’s not closed yet, that is an excellent and interesting place to hang out and peruse and is connected to the Disneyana store as well which is always so fun to peruse. If that is closed then Tiki Room and the Castle Walkthrough will be your only other indoor walkthrough attractions. For rides with an indoor or covered queue, the Fantasyland dark rides except for Alice, Buzz, Star Tours, Space, Nemo Subs, Millenium Falcon and Rise will be good ones to head for cover. If you have a Visa card you could so go see if the meet is happening in the Star Wars Launch Bay, but they don’t have anything else open in there, I don’t think.
Then in DCA the rain will drive a lot of crowds ot the Animation Building but if you wanted to do it anyway, then there’s a lot in there you can do all at once to divert yourselves for at least an hour: Animation Academy, Turtle Talk with Crush, Sorcerer’s Workshop, Anna/Elsa meet and the lobby itself. It’s also attached to an art store, Off the Page which is fun to peruse. And across the street from the Philharmagic which is always cute to see and has a lot of capacity to absorb those seeking cover.
I do feel like you have a good setup for most of your plan, Wine Country Trattoria being the one exception for not quite being ideal in rain. Storyteller’s and Hearthstone Lounge right in the Grand Californian next door might be good alternatives to check (but Hearthstone doesn’t do reservations). Plus you can wander the Grand Californian lobby to also keep out of the rain. Just note you will be exiting the parks security perimeter by entering the hotel so when you come back into the parks (or downtown Disney) you’ll have to redo security. And the lines out of the Grand Californian can get backed up easily so it can take an extra 10 or so minutes if it is.
It snuck up on me for lots of reasons, including my DH being an VA employee and lots of uncertainty about his job. We’ve considered canceling but have decided to seek some joy where we can find it. Hopefully we can find it in the rain, as 2 of our 3 days are forecasted to be very rainy.