WOW! That is one tough choice!
Does you little girl love to swim? Is she a real little princess that loves pretty things and to dress up? Then I would choose the GF. Is she a bit of an energetic tomboy and loves 'cool' things like a monorail going through 'her' hotel? Then I would choose the CR. Is playing in the sand something that she would love? How about watching fireworks while in the pool? Do you plan much time in Epcot? Then I would book the Poly.
Don't forget considering the theme that Mom and Dad will love. usually the children are happy wherever the parents are happy. Have a look at picturewsw online to see if either theme really resonates with you.
Most people really enjoy the Poly, so it is a default choice that is usually positive.
All three are tied for my favourite resorts in WDW. FWIW, my first trip that I took my 2 grand daughters to WDW we stayed in the CR tower, TPV and we all LOVED it. This year I am taking my 2 grand sons to WDW for their first time as well, and we have chosen to stay in BLT. So, if my choices are anything to go by, I guess that the CR is my vote! Although it really depends upon what you are looking for in your hotel. All three are great but give very different experiences.
Good luck choosing!