Congrats! We're doing a vow renewal too. We had originally planned on the $29.95 drive thru special in Las Vegas, but then we thought the kids wouldn't appreciate an Elvis impersonator as much as they would Mickey Mouse. But man oh man, did the budget ever explode! WDW used to have a "rehitching ceremony" I heard at some Sundae place, just a really simple vow renewal. I would have totally been into that, but they canceled that policy.
Escape (aka Intimate) Weddings are the least expensive way to go if you want an official Disney Wedding. There are also ceremonies available at the Swan and Shades of Green (for military families) and other Orlando venues which are far less expensive than Disney. Honestly I don't think that you'll be able to have a ceremony in front of the Castle (which is what everyone dreams of when they think "Disney wedding"). I only know of one DisBride who did that, and she had to jump through a ton of hoops, and do it at off-hours. But if you do book a Disney wedding, you are allowed to book a photo shoot in front of the Castle (I think it costs about $1100 extra) very early in the morning. With the Escape package you get a choice of 5 set venues, a violinist, a bouquet, a boutinerre, a cake that feeds 20, a champagne bottle that feeds 6, 2 annual passes, four hours of limo and a Disney photographer and 2 5x7 prints.
You have to pay for your own officiant ($150-$250) and any kind of reception/dinner you have. We're doing a sand ceremony too ($25).
Good luck with all your planning!
Jil