If total travel time eating into park time is the concern, I'd say to do the early breakfast at 1900PF. Bus from CBR to MK; resort loop monorail or boat launch to GF - if the boats are running that early, that's the fastest option. Afterwards, monorail from GF to TTC, then change to the Epcot monorail line to Epcot.
But you will not get to Epcot until at least 9:45, maybe even 10 am.
If getting the Epcot FPs is the bigger concern, I'd say go from CBR straight to Epcot well before RD (especially since they are no longer doing "RD" at Epcot; you need to be at the front of a turnstile line before the park opens). Grab 1 set of FPs. Ride something. You'll need to be out of Epcot before 10 am to take the monorail from Epcot to TTC, then transfer to the resort monorail line to GF for a 10:30 breakfast. In effect, you are making this an early lunch break. You probably won't get back to Epcot until 12:30 or so.
Final alternative, of course, is to go to 1900 PF for dinner instead........ Completely different set of characters, though. And there are so many good dinner options right there in Epcot. Decisions, decisions.........
