Atlantis

Can you purchase wristbands anywhere other than the cruise ship?

If only the kids are going to use the watersides, is there a way to purchase the aqua excursion for them and just the discover Atlantis for the Adults?

I also saw Resort for a Day offers a package. Has anyone done this?

You can buy passes thru Atlantis or Comfort Inns (the sister property)...you don't have to go thru the ship I don't think you'll be allowed into the pool area with your kids if you don't purchase the pass.