Hi Danielle!
Nine days is excellent - you can enjoy the parks slowly, take breaks as you need them, explore outside the parks, and enjoy the pools and amenities at your resort.
With children the ages of yours, I would definitely make sure that you take your time and try to stick to your daily routines, such as naps and meals, as much as possible. This helps the children enjoy themselves better without getting so tired and cranky, and therefore everyone enjoys their vacation much more!
I would like to suggest that you plan to spend at least one day in each park, and then allow
at least one more day to go back to the park you choose as your favorite in order to visit the attractions you missed the first time around, and/or enjoy your favorites once more.
I would also allow a day off between park visits as often as possible to allow everyone to recover and rest up for the next park day. Swimming has always been a favored activity within my family. We also enjoy exploring all of the different Disney Resorts, and going to Downtown Disney & Marketplace to shop and dine.
For your anniversary, I suggest you check out some of the special options available for celebrating on the Disney website by clicking
HERE.
You may also want to check the children into a childcare center, such as the Neverland Club at the Polynesian Resort while the two of you enjoy a romantic experience all alone, such as the Spirit of Aloha Dinner Show there, or Victoria & Albert's at the Grand Floridian. Or how about a private specialty cruise? Learn more
HERE.
I hope this is helpful! Happy Anniversary & Happy Vacation!