We're also going (again) next year!
We've done it several different ways, all with their own benefits and disadvantages:
VRBO villa, plus car.
VRBO villa, used Uber and Lyft.
Disney's Saratoga Springs resort, dining plan, no car.
x2 maisonette-style villas, shuttle service, no car.
Conclusions:
For us, as a family, we prefer the villas booked through VRBO, with park tickets and flights booked separately. We found hiring a car to be unnecessary, even to go shopping at the malls or to go out to eat in the evenings- Uber and Lyft worked really well, and of course meant no car park fees or rental costs. Plus, no-one had to drive.
The year we stayed on Disney and had the dining plan was the year we had the Olympics here, and there was a never-repeated 25% discount. It's too expensive normally. The dining plan was great, but we did end up wishing we had gone outside of Disney to other places.
Transport around Disney itself is easy and plentiful- if you have a car you can drive to one park, park there, and use the transport system to hop to other parks.
The two places that had shuttle service were ok, but mostly the shuttles were at inconvenient (for us) times, and were nearly always crowded.
I book flights in December at the latest. Usually BA direct, although last time we split the journey and knocked a couple of hundred each off the price. It made for a very long day of airports and flying though.
You need to decide if you want to share a hotel room, or want a bedroom each, how you want to get around, where else you want to go etc.
The cheapest option for us has been the villa/no car option, but we're a family of four who all want our own rooms.
IMO the best time to go is the latter half of August. Somewhat cooler, although rainstorms happen sometimes, and the crowds are ever-so-slightly thinner.
Edited to add: a car is a good way to get around, but gets unbelievably hot in the car park upon your return. Also, make sure you do something to identify your rental car to make it stand out from the hundreds of identical ones, so you're not left wandering around zapping cars with the remote control thingy (voice of bitter experience)