The boat dock is by the windmill in front of the BC lobby, well, over to the right a bit, as you face the water. The boat will take you to the back entrance of Epcot (WS) if you wish, but really, you could walk from the back entrance of BC to that entrance faster than any boat will take you, (because the boat will first stop at BW) and the walk will be about the same. The walks that I am talking about would be from the BCV to the World Showcase entrance of Epcot, or the walk from the BCV to the boat dock at the BC.
I'm guessing that there's a boat in each direction every 20 minutes...maybe less at times.
If you want to go to DHS, the boat goes from BC to S/D to DHS. This will be faster by boat than the walk would be for most people most of the time. I guess that the boat takes 15/20 minutes.
Those boats run from DHS, to S/D, to BC, to BW, to WS entrance from Epcot, and then reverse the stops. Epcot, BW, BC, S/D, DHS.
Bobbi
PS. Have a great time. Our next all family vacation is in November and we're staying at BCV for our first family vacation there, and we are looking forward to visiting those parks. It will be the first time our DGC will be visiting them as well. So far, they've only done AK and MK.