The best way to get back and forth to the BW from the All Stars is to drive. The BW has free parking available for its guests. You can also take advantage of the valet service for $6 plus tip.
If you use Disney transportation, the best way to go is to hop the bus going to MGM. You'll need to go to the BW before MGM closes for the day. From MGM, take the boat to the BW. The boat dock is to the right of the MGM entrance (the right as you face the park entrance). You can also walk to the BW from MGM (but I wouldn't recommend that with three young children). The path begins across the canal from the boat dock.
Most likely, you will be leaving the BW after MGM closes. (If the park is still open, then just reverse the directions above). From the BW, you take the bus to DD and then transfer there to the All Star bus. Be prepared for this to take a while - up to an hour to get back to your hotel. If you are OK with your children riding in a taxi without car seats, this would be the quickest way to return. I would estimate it to cost $12 -$15, including tax. (BTW, if I recall correctly, taxis are exempt from the FL law that requires children to be in car seats). Both the bus stop and the taxi stand (just ask the CM at the desk near the driveway to call one for you) are on the opposite side of the Hotel from the boat dock.
Hope that's enough info to make your decision. Enjoy the trip!
