You are in a for a great time!! You just need to have a game plan!!
These are some books that are REALLY good and geared towards touring the parks with kids!!
this one is my favorite-
-The Unofficial Guide to Walt Disney World with Kids 2012 (Unofficial Guides) by Bob Sehlinger, Liliane Opsomer and Len
This is also a good one and fun for kids!
-Kid Tips for Walt Disney World: Touring Advice by Kids for Kids by Tracie A Cook
I think the biggest mistake people make in doing Disney with kids is to allow the kids to call all the shots and run their adults ragged. The whole "You are there for THEM and not for YOU" mentality doesn't tend to lend itself to happy touring days. You and your husband are not just there to be money and food dispensers. You need to make sure you are having a good time too. If you have a plan that works for EVERYONE, then everyone will have a great time!! If you have your day kind of "mapped out" you will have a loose structure to your day and won't be standing around trying to figure out "what next".
It might be a good idea to figure out what kinds of kiddos you have...meaning are they timid about rides? The dark? Characters? etc. That way you have a bit of structure as to what kinds of things will be the most fun. The worst thing would be to have no clue that say Haunted Mansion would scared the daylights out of one of the kids and then you spend the rest of the day dealing the fallout from the emotional trauma!
Make sure you that your pace works well for shorter legs! There is nothing wrong with renting a "kid transporter" if the little one is not handling the pace well. (ignore the haters about kids over the age of three in "strollers". Disney is not normal walking. It can be up to 16 miles in a day depending on which parks you go to. So do what works best for your crew and ignore the stories of others children and their superhuman feats of never needing to rest OR go to the bathroom let alone ride in a stroller!
It is an option that you have and it can be a lifesaver!)
It's important to remember to hydrate and keep blood sugar at an energy sustaining level. I always carry goldfish crackers and Zbars in my Disney bag to hand out when kids are flagging energy wise. Zbars are organic and have protein and they work WONDERS. They are made by Clif bars and have several flavors! You can get them at Target.
Mister fans are great for keeping little bodies cool and if you buy them before hand you won't have to pay the outrageous Disney prices!!
Rest in the middle of day when it's the hottest if you are able to do so. A mid day pit stop back at the resort to swim and rest and rejuvenate will do wonders for the second half of the day!!
Lastly-It's important to have expectations in place for behavior as well. Sometimes kids will push boundaries to see how far they get with adults that are not their parents. So talk up front with the kids about your expectations behavior wise. Everyone needs to be respectful of each other (kids to kids and kids to adults) and make sure nice manners are packed along with every thing else! If the kids are misbehaving and nothing is done to correct it you may be in for a frustrating day.
So long story...long...have a plan in place. Know what your game plan is for the day. Correct what needs correcting and be flexible when you need to be.
The kids will take their cues from y'all! If you are having fun and are in control, they will have fun and be able to relax.