Hi Samantha ~
Those 3 awesome resorts and you certainly can't go wrong with either. Think about which parks you think you're going to spend the most time in during your trip.
If you think you'll spend the most time at Epcot and Hollywood Studios, it would certainly be more convenient to stay at the Beach Club. Its one of my favorite resorts at Disney. Concierge Level is amazing and would be incredibly nice since it would save you some time running around for breakfast and snacks when you'll have an 8 month old. If your baby is sleeping, one of you could run to the Concierge Suite to bring back food and drinks. The Beach Club has great amenities including the best resort pool at Disney. It tends to get crowded during the summer months but there are quiet pools you can relax in as well. Here are some other
reasons I love the Beach Club Resort.
If you think you're going to spend more time in the Magic Kingdom, I would stay at the Contemporary or the Polynesian Resort. With an 8 month old, I would go with the Polynesian. We felt like the rooms are bigger and it would give you more space for a Pack 'n Play. My boys loved the Volcano Pool but there are quiet pools if that is more your style. You can also see the Electrical Water Pageant and Wishes from the beach. We liked the dining selections at the Polynesian. 'Ohana is awesome for breakfast and dinner. For quick serve, Capt. Cook's has a nice selection including the famous Tonga Toast at breakfast and Dole Whips all day.
Both the Contemporary and Polynesian are on the Monorail line and offer easy access to the Magic Kingdom and the Epcot Monorail which is a incredible perk. I love both of these resorts but when I have my family with me, the Polynesian Resort seems a little more low key and family friendly.
Wishing you minnie magical memories :-) Allison V.