Another family of 6 here! We go annually and by far, your cheapest onsite option is two value rooms. For this fall, you can get a value room for $100 through Disney and even less through the third-party sites like Orbitz or Cheaptickets.
The dining plan is no savings unless you can get it for free but then you pay rack rate for the room so you really need to weigh those costs in terms of how much your family eats, are you willing to compromise some on meals such as older kids or light eaters ordering from the kid's menu some or sharing meals. We really like to snack our way through WDW so we share or do kid's meals a lot. "
Free dining" isn't really free. It isn't necessarily the best discount for everyone.
There are ways to get discounted Disney GC's which can be used to pay for everything you would pay Disney directly for and can also be used if you go through a TA. The discounts are not huge but we all know that DIsney is expensive and every little bit saved helps.
I am also a SAHM. There is simply no way we could afford Disney without me making the effort to save everywhere I can. I shop sales, use coupons and we eat out very, very little. I cook at home 99% of our meals and many times we do 'budget' meals for a couple of weeks just to add more money to our Disney fund. I was raised by a single mom so I know how to cook inexpensively. We drive old, long ago paid off cars, shop thrift, don't have cable and we have pay-as-you-go Tracfones. You may already have trimmed your budget as much as you can or that may not be something you are interested in but I am just sharing how we afford an annual WDW trip. We also have an automatic bank transfer every month so that helps our WDW money never to get spent elsewhere.
It's difficult, imo, as a single income household to take a big vacation every year. I cannot imagine trying to save that amount of money without my dh on board. Maybe yours will come around.