1900 Park Fare has always been the slowest character meal for us. I think it opens at 4:30 for dinner, so I don't think you will get there any earlier. Hopefully you will seated immediately since your ADR is for 10 minutes after they open. I would actually get there at 4:20 (they typically won't let you check in there until 20 minutes before your ADR), and maybe you will get seated right when they open. We have had an ADR at 5:00 before, and even that early, the shortest wait we have ever had was 20 minutes after our ADR. We have had to wait over an hour after our ADR to get seated there. The characters sometimes get very spread out and it can be slow getting them all to your table. Again, if you are one of the first tables seated, it may not be that way for you because they may start right around where you are and work their way through.
For us, I don't think we have ever gotten out of 1900 earlier than 2 hours after our ADR (and it has been later more than once), but again, our earliest ADR has been 5:00 p.m., so maybe you will get lucky. I recall one year we had a 7:00 ADR and we hoped to make wishes at 10:00 at MK, and we were still in 1900 Park Fare when Wishes started! We went out and caught the last half from the GF dock. We waited over an hour for a table that visit.
It can also be slow getting buses from GF. Bus service has been our only complaint each time we have stayed there. You might get lucky and get to the bus stop right when the DHS bus gets there. We have actually waited an hour for a bus more than once outside the GF, and we have waited 30 to 40 minutes many times. Again, it is all going to be pure luck. It is about a 15 minute drive once you are on the bus. You could try to take a cab. We always think maybe we will just take a cab, but we are always sure that bus is just another minute away. I don't know if they still have it, but last time we stayed there they had a board that showed you when the bus would arrive--- don't believe it. It would tell us the bus would be there in 5 minutes, and then we would just watch the board change the arrival time over and over.
You would pretty much have to have perfect luck on everything to make it. Even if you are out of 1900 by 6:00- getting a bus, getting to HS, getting through the gate, walking in and getting to Fantasmic may not happen in an hour. Plus, you would have to just hope that Fantasmic was not full by the time you got there. You can have a loose plan to try it, but make sure everyone knows not to be too upset if it doesn't happen. Good luck. I hope it happens for you.
