You should be fine. We went to DHS about a month ago, on Saturday March 19th, for a few hours before heading to Port Canaveral for a cruise. It was a triple whammy day -- morning EMH, Fantasmic night, and right in the middle of spring break. Still, we got quite a bit done.
My DH was close to the front of the line for rope drop (which was 8am), and he immediately got TSM fast passes. We all then rode TSM standby (about a 10 minute wait), then went to ride RnRC, which was not working, so we rode ToT instead (about a 20 minute wait to get to the preshow). We then got a fast pass for ToT and rode RnRC (single rider, about a 10 minute wait), went through One Man's Dream (but did not watch the movie) and rode TSM with the fast pass. We stopped for a snack at Starring Rolls before using our ToT fast pass.
We then left the park around 11:30am. If we could do all of that on such a busy day, I think that you will be fine. Just get there for rope drop, have a plan, and realize that you can't see everything so enjoy what you can do. Have fun!