Rylee beat me to this: I was just about to ask if you have a significant other (or adult friend who's helping with the kids). If so, the seven of you won't fit in a Fort Wilderness Cabin unless you put the 3-year-old in a crib and convince Disney that s/he is under 3.
Your cheapest onsite option would appear to be two connecting rooms at a Value resort. Each room has two double beds, so two rooms will sleep eight. You'll also have two baths. (The Family Suites sleep only six, the same as the Cabins.) Some people love the Values, others can't stand them. Watch some videos, at YouTube and elsewhere, and see what you think.
If the Values don't appeal to you but you won't fit in a Cabin, consider renting DVC points to get a "value" two-bedroom lockoff at Animal Kingdom Villas. (Disney terminology can be confusing. "Value" here has nothing to do with the Value resorts. The "value" rooms at AKV were converted from hotel rooms and are a bit smaller - and cost significantly less - than standard Villa rooms. "Lockoff" means that the two-bedroom is made up of connecting one-bedroom and studio units.) There are DVC units at several other WDW resorts, but the AKV value units are the cheapest.
For a little more money than a Cabin, an AKV value two-bedroom will give you nearly twice the space and a lot more amenities. Here's a comparison:
Size
Cabin: 504 sq ft
2BR: 945 sq ft
Beds
Cabin: Bedroom with 1 double and 2 bunks, living room with 1 double (= 6)
2BR: BR with 1 king, BR with 1 queen bed and 1 full sofabed, LR with 1 queen sofabed (= 8)
Misc.
Cabin: Full kitchen, 1 bath, 1 TV with DVD player, deck with picnic table
2BR: Full kitchen, washer & dryer, 2 baths (1 with Jacuzzi), 3 TVs (1 with DVD player), balcony with small table and chairs
Surroundings
Both Fort Wilderness and Animal Kingdom Lodge/Villas have great theming and landscaping, and both resorts have a variety of activities geared to children, families, and adults. The food is said to be better on average at AKL/AKV, although some (but certainly not all) of the options are on the exotic side.
Cost for 1 week in shoulder season
(i.e. not school vacation or holiday period, but not dead of winter)
Cabin at rack rate: $2722.50 (including tax)
Cabin at 20% off: $2178 (again including tax)
2BR via broker: $2860 total (no tax on point rentals)
"Broker" is someone like David's Vacation Club Rentals (
http://www.dvcrequest.com), a sponsor of this board. You can rent points directly from a DVC owner for a little less, but there's a trust issue involved. (You can also book DVC Villas directly through Disney like hotel rooms, but the cost is much, much higher.)
For comparison, two rooms at a Value resort at the same time of year would give you 520 square feet and cost $1775, or $1420 if you can snag a 20% discount. (These rates are for Pop Century; the tax at the All-Stars is a hair more because they're in a different county.)
I hope all this information is more helpful than confusing. Let us know if you have questions. Again, watching videos of the different resorts will give you a feel for them that you can't get from words alone.