Hi tooraloora, welcome from a fellow Canadian
First off, if you decide on the cabin, you definitely won't be roughing it. The cabins come with a full bath, A/C, heating, refrigerator, stove, microwave, dishwasher, coffee maker, 2 TV's, VCR etc, not to mention daily maid service. We have stayed in the cabins 3 times (and the wilderness homes before that) but have also rented pool homes in Kissimmee (Chatham Park) quite a number of times. Obviously, the difference in price is a factor but you will have to rent a vehicle if you decide on a rental home. Some of the shuttle services from the airport will stop at a grocery store to allow you to pick up groceries on the way to FW. You can also pick some things up at the Trading Posts in FW but it will cost you more. The cabins will sleep 6, so you will be ok. They are not excessively large or anything, but from my experiences, you won't be spending a lot of time inside the cabin anyway.
Having stayed in the cabins and at the vacation homes, the choice is very easy for me to make. There is no feeling like staying in Disney and especially FW. I have two young children (5 & 6) who enjoy FW as much as any of the parks. They ride their bikes, play on the playgrounds, go on the pony rides, see the animals at the petting zoo, fish in the streams along with many other things. This is something that you don't get at a rental home and it's hard to put a price on it. For us, the difference in price is worth it, especially with the kids. In previous years, we would stay at FW for a week and then at a rental home for a week. The homes were very nice, but there was such a letdown once we left FW, you could just about classify it as depression
. The rental homes are just not the same...
My recommendation would definitly be FW. Your week will go by before you know it and with the ages of your children, I don't think you can go wrong.
I'd be happy to answer any other questions you may have.
Jeff