The on-site hotel prices are ridiculous. If money is the concern, definitely stay off site. You get so much more for so much less money.
If you have small kids, you'll love HIFS! I just posted about the great rate I got yesterday. Under the title "Great rate at HIFS" or something like that, lol! It's farther down on this page.
We stayed there last year and returned every day for our youngest DD to take a nap. It was very quick and easy!
Good luck with your decision,
Teresa