That's a good suggestion, NJ2, but what might make even more sense (again, depending on the time) is for the OP to take a bus from the All Star resort to MGM, then the Friendship boat from there. While Epcot is a good idea, that would involve walking all the way through that park. With MGM, the OP can just step off the bus and walk directly to the dock. In fact, even if MGM closed within the last hour or so, they could ask a driver dropping off Guests from that park if she or he is heading directly back there to pick up more passengers. And of course, if it's an EMH night at either park, that makes the whole 'getting there' scenario more relaxed.
Now, getting back to the All Stars from the Boardwalk, odds are the options will be much more limited - most likely either a cab, or a bus to Downtown Disney and another bus back to their resort. Or, if Epcot's the EMH park and they don't stay at the Boardwalk too late, yes, they could walk through Epcot and grab a bus straight back to ASM.