You are getting lots of good advice!
These are exactly the 3 resorts we have been fortunate to stay at, and we loved each one. You really cannot go wrong. The GF was first, and to be honest, I think our hearts belong to the GF, in a way. We also love eating at Narcoossee's and Citrico's (esp. standing out on the dock watching Wishes after a good meal at Narcoossee's!). We love sitting in the lobby having a drink and listening to the music. We also enjoy the boat transportation to MK, Wilderness Lodge (for dinner). Some call is stuffy, but I can tell you, my boys feel totally comfortable there.
But...when I took my twin DS12 (then 11) and their friend, on my own, I could see how much the Poly theming and pool appealed to them. And, with one of the boys in a wheelchair, I loved the easy access to both monorail routes (less pushing up and down ramps!). As the only adult wrangling 3 excited boys, making the transportation easy was a big plus.
And then...in March we had our first brief stay at the Beach Club, and I know we'll be back! The boys absolutely LOVED Stormalong Bay, Beaches & Cream. And their favourite park is Epcot, so the convenience of walking over to the International Gateway was fantastic (we were just there for 2 nights before a cruise, so we just went to Epcot).
One of my boys is home sick, and I just asked him which of these three he likes best...he says the Beach Club!
However...I do think you should listen carefully to your mother's wishes. If the GF will be a dream come true, then why not make it a special trip for her and stay there? We planned our first trip like it might be our only one, but somehow we've had 3 more...