Maxtrix, I would call down to the hotel directly and get their shuttle's schedule to the various parks, shopping etc. and also check out the Lynx bus schedules on their website. On a night that you will be out late you could take a taxi back to your hotel.
We stayed at the HOJO Maingate East on 192 during March Break 2001 and since dh used the car to go off golfing everyday, the kids and I relied on the hotel's free shuttle. Although there was a set schedule, they ran late enough to allow for the fireworks etc. and worked out well for us. We just made sure we were at the pick-up point early enough to get on the first bus out in the morning and they made sure that those of us that stayed late for the last bus, all got back to the hotel. Drop-off point in the morning was at the TTC and you took Disney transport from there and there were two pick-up points at night ~ TTC and EPCOT. Certainly not as convenient as having your own car, or staying on-site but it was doable.