Anyone can do character dining. You don't need a meal plan or an on-site stay. If you are looking at budget-friendly options, you might look offsite. I know the Swan (boardwalk area) has character dining that's much less expensive than on-site options. When we stayed there, we saw Minnie and Goofy at breakfast with no ADR; just walked in. There are some Disney spring restaurants that also have character dining for less than on-site
Dining plan is a terrible idea if you're on a budget. Everyone in the room has to be on it, and your 11-year-old will be charged as an adult. Unless you are doing character dining daily and drinking a lot of alcohol, the dining plan will not pay for itself. But if you're budget-minded, you're probably not someone who is going to do character meals every day. Plus, don't underestimate how much time those meals eat up; you'll lose 1-2 hours of park time for each. You can pay out of pocket for a few nice meals, and you'll still come out ahead. Most Disney meals are a lot of food. Unless you're at a buffet, you can save money by sharing entrees, having an appetizer instead of an entree, and/or ordering a child's meal. As an adult, I was quite satisfied with children's meals on our last trip.
Offsite CAN be a money saver, but it depends on how you do it. Renting a car and paying $25/day to park will eat into your savings rather quickly, though there ARE bargains out there. Especially if you look into some of the timeshares, you might be able to get a bargain that still brings you out ahead. Additionally, if you're in a unit with a kitchen, you can save quite a lot preparing simple meals, or just using the car to eat at non-Disney-priced restaurants. Others use a combination of Uber/Lyft and hotel shuttle to avoid renting a car. Especially if you're one to spend all day in the parks without going back for a midday break, Uber/Lyft would probably be on par or less than the parking fee. On the other hand, an All-Star is certainly less work than figuring out the options, especially if you're not already well versed in priceline, hotwire, etc.
One problem with All Star Sports is it hasn't been renovated, so you'll have 4 people in two double beds for 5 nights. It is a small space with small beds. My family would not sleep well under those circumstances, and we'd be crabby as a result. Your family might have no problem with that arrangement, but being squished for a week is different from sucking it up for a night or two. Even if offsite doesn't give you much in the way of savings, it can give you a lot in the way of space.
A compromise might be to look at Disney Springs hotels. The DS hotels are generally nicer than the All-Stars (indoor corridors, queen beds, etc.), so you might find greater value in the accommodations. Especially if you look at discounted websites like Priceline, you can usually find some options that are less expensive than All Stars, even after adding the dreaded resort fees. DS hotels have reliable transportation to/from the parks, so you don't need a car, and you get the 60-day fast pass booking window and extra magic hours. The catch is, you need to get yourself to and from MCO; an Uber will cost about $40 each way.
Purely from a personal stance, if I'm traveling with my husband and kids, we stay offsite and rent a car. If I'm going to Disney myself with one or two kids, we'll stay value or Disney Springs to avoid the costs of car rental and parking.
