Hi Karen,
You are choosing between three great resorts!
Disney's Polynesian Village Resort has a lush and tropical theme, and has a monorail stop right at the resort. For a sweeping lobby and feeling of rustic, Pacific Northwest grandeur, you cannot do better than
Disney's Wilderness Lodge.
Disney's Beach Club Resort has a charming seaside theme, and the amazing Stormalong Bay pool is not to be missed!
Considering that you will be spending the most time at Epcot, Disney's Hollywood Studios, and Disney's Animal Kingdom, I recommend Disney's Beach Club Resort. You can access Epcot with a quick walk from this resort! You can also walk to Disney's Hollywood Studios, though that walk is a bit longer. Boat service is also offered from Disney's Beach Club Resort to both of those theme parks. Disney's Polynesian Village Resort and Disney's Wilderness Lodge are both closer to Magic Kingdom.
You mention a concern about how relaxing Disney's Beach Club Resort is. I have always found it to be quite relaxing! Is is located right next to Disney's Yacht Club Resort, but I have never found that to make it feel overwhelming as both resorts are not too huge. These resorts are located on Crescent Lake, along with Disney's BoardWalk, and nearby the Walt Disney World Swan and Dolphin hotels. Again, I have never found that to make this less relaxing; to the contrary, I like being able to walk to other resorts to experience their shopping and dining! As I mentioned, I love the Stormalong Bay pool area with its waterslide and lazy river; however, if this is overwhelming, you can always head to one of the less-crowded quiet pools at the resort.
I hope that these thoughts are helpful for you, Karen!