Hi, Tiffany! Staying at any resort on the monorail is extremely convenient. You really cannot go wrong with any of the choices!
The
Contemporary is slightly more convenient because you can walk to the Magic Kingdom. If you want to go to Epcot, you just go one monorail stop, switch monorails and you are off to Epcot! The Contemporary is also home to Chef Mickey's, a great dining choice for your twins!
While you cannot walk to Magic Kingdom from the
Grand Floridian, it is just one monorail stop away. There is also a boat that shuttles guests between Magic Kingdom and Grand Floridian. With your girls, you will probably want to enjoy a meal at 1900 Park Fair. The pools here are amazing. This is one of my all-time favorite resorts!
If you are leaning toward the Grand Floridian, go for it! Make sure to take a monorail ride over to Contemporary and Polynesian during your stay so you can see your options for your next Disney trip!