We love and own at Copper Creek so I'm biased, but before buying in to DVC, Beach Club was one of our most frequent deluxe Resorts just because we spend so much time in Epcot! The Beach Club pool is incredible and no other property comes close, BUT Wilderness Lodge has two wonderful pools, and a really fabulous kids play area. And the lobby is 1000x more kid friendly than most other Disney resorts. Don't even try to count how many times my kids will run back and forth over that bridge.
It's not in the title, but you briefly mentioned Boardwalk. Okay, I'm sorry to the Boardwalk lovers out there, but I really don't like anything about that resort except the location. And the pool is the worst of those 3 options for young kids. There's one good waterslide but overall the pool isn't even in the same league as the other two resorts. The 8 year old would have fun at any of the pools, but a 3 year old can't do much at the boardwalk pool unless they're able to swim or just like hanging out on lounge chairs.
Editing to add a few more thoughts. You also mentioned Saratoga in the title. I haven't been there since pre-kids so I don't have great advice but the biggest drawback is size and location. You're gonna be doing a lot of walking at the resort and the bus rides to the parks can take a while. If you have an option to book Copper Creek, take it. It's actually becoming one of those resorts that are really hard to get at 7 months, especially in fall/winter since it has that perfect cozy woodsy feel.
So bottom line, if I were in your shoes, I'd book CC at 11 months, wait-list BCV at 7 months. Both are great options and you can't lose.