With the ages of the kids, you can probably still get by with a room for 5 at Port Orleans Riverside...as long as one of the kids comfortably fits on the pull down bed (it's about 63" long) and the other 2 kids can share a queen-size bed. Our kids are tall and would never have comfortably fit on that bed past the age of about 9. And while they can share a bed for short trips (a night or two), on longer vacations they do best if they each have their own bed as they're all restless sleepers and don't sleep well when sharing a bed.
We've traveled to Disney as a party of 5 on several trips and we prefer a suite at Art of Animation or prior to that resort opening, we got 2 rooms at a Value Resort (usually Pop Century). But we're willing to pay the higher price for the extra space and 2 bathrooms and I realize that's not an option for everyone. While we don't spend a lot of time in the room, it's nice (for us) to have two separate sleeping areas as our kids tend to stay up later than my husband and I while we get up earlier than the kids. We also like the extra space for storing luggage; the microwave for heating up snacks and leftovers; and a table to sit at to eat breakfast.
One room at POR is the most economical on-site choice if the logistics of those rooms (pull-down bed, one bathroom, etc.) work for your family.
As far as other tips, we skip the dining plan and just pay out of pocket. We don't eat the way we would need to eat to make any of the dining plans a good deal for us. We've tried to QSDP, but still had meals and snacks left over at the end of the week. We usually only do one or two table service meals because we can't decide where we want to eat dinner tonight let alone 6 months from now. I often eat a kids meal because that's more than enough food for me. Same with our teenage daughters. Sometimes we even just split a few meals between the 5 of us -- not to save money, but to avoid throwing away more food than we eat. A lot of people bring their own snacks and water to the parks to save money. We don't, but that's definitely a way to save money -- just bring water and snacks with you if you drive or have them shipped to your resort if you fly.
