We've done both - and I would suggest dinner at GF.
You get to see Cindy, plus mice, FGM, and Prince Charming. If she is a big fan of Cindy+ this would be the one.
As well, you will be able to get a PS easily and won't have to go through the stress of getting a PS at CRT at 60 days.
I found dinner much less hurried, it's a buffet so you can take you time and have good selections for everyone (even those picky eaters) (Don't forget to try the strawberry soup) and the kids buffet is nice.
My advise would be try to get an early PS (ours was 5:10pm) to get right in and seated. All the characters came by our table twice, and FGM is outside in the hall. We just waited until she didn't have a line, went out to see her, then back in for desert. DH stayed at table (and kept eating!)
The atmosphere in the castle is nice, but I much preferred the more relaxed setting at 1900 Park Fare. As well we didn't feel it was worth the $$ for a bfast that was preplated. Even though it was nice at CRT, I felt they wanted us in and out as soon as they could. (We had first PS at this one too)
At GF, since we ate early, we just went over to MK for the evening.
I hope this helps