Thanks Kook & everyone for the transport advice. Better to know now. Maybe we'll do the boat the first day since we arrive at lunch time (assuming we can eat snacks on the boats) and try the bus for our early Epcot day.
I did a search for boat times, and it looks like it's around 10 minutes from WL to CR - is this accurate? So is it about 30 minutes for WL to MK?
Our experience in September with low crowds was that times on the boat were about 15-20 min to MK and 5-15 min to Contemporary. For the Contemporary, it depends on whether the boat is going to FW 1st or not, which adds about 10 min to the trip. They run the boats both directions, so the Contemporary will either be the first or second stop on the boats that run between WL, CR, and FW. If CR is 1st, then it is only about 5 min on the boat.
In addition to the times above on the boat, you have your wait times for a boat. We usually only had to wait 5-10 min for a boat, but I'm sure at times these waits will be longer. In general, we allowed half an hour from leaving the room to being at the entrance to MK.
Once you are at CR, your travel time to Epcot is the same as a CR guest. The walk from the dock to the lobby at CR is shorter and flatter than at WL, so it really isn't too bad. Once you get to the lobby, you have to get up to the main level and then up another half floor to the Monorail, so you can either take two escalators or two elevators. Then you will have to change monorails at the TTC, which involves going down and back up a ramp.
If you do the boat to MK option to catch the monorail there, you will have more time on the boat but then can take either monorail option to the TTC. If you choose the resort one you will first stop at CR, but the express one will take you straight to TTC first stop, where you then transfer to the Epcot monorail.
Like WDWKOOK mentioned, we found busses to Epcot to be the faster option, but we certainly did both. Our preference was to start with the boat / monorail and then bus back once we were tired, but part of the fun is having options, trying different ways, and finding what works best for your group. Even though busses aren't my favorite, it is really nice to have that option, and we took advantage of it. I see this as an advantage of WL, since Monorail resorts don't usually have an Epcot bus option. Just consider the travel time part of the fun and enjoy it with the rest of your trip, after all, you're at Disney. Enjoy!