You have to take your luggage with you unless you are flying an airline that allows you to check in at your resort. They weigh the backage right there just like if you were at the airport. If your airline doesn’t participate, you have to take your luggage with you on your trip back to the airport.
When we flew Delta last year, we went to the ME desk at the Beach Club to check in our luggage. They have a scale there. The CM weighed the bags and 1 was over, so DH offered to take the bag back and move some stuff to another bag. The CM said not to worry about it and let it go and didn’t charge us.
I’m not sure if that is the norm. But you will know when you check in at the ME desk if your bag is overweight b/c they have a scale there.
They aren’t, you’ll just have to take your luggage with you under the bus. We’ve done it several times and it’s easy, someone will load your luggage on the bus and there’s usually several sky caps waiting as you get off the bus at the airport to help you with your bags if you need it.