We have stayed Poly Club level and YC club, although not BC. Both were great, but my kids would pick Poly hands down. Everyone’s opinion differs on the value of club level and we’ve certainly done trips without it and survived just fine. But if it is in your budget, I think the convienence is worth it. You can watch the MK fireworks from the club lounge at Poly. So we would often come back from the parks, get the kids in their pajamas and then eat dessert in the lounge and watch the fireworks.
As far as the actual hotel, you are so close to MK, which is great with young kids. If you’re interested in a character meal, the Ohana character breakfast is one of our favorites.