TP also says a 7. So, yes, that will be a crowded day in DHS. But all is not lost. That just means you need a good plan and reasonable expectations.
Getting there at rope drop will get you into Jedi. But how close you are to the front if the line determines what time. Getting into the first show will give you max flexibility the rest of the day. But that means getting there by at least 8:15 ( for a 9am start).
What else is on your plan? How are you planning to handle Toy Story Mania?
Also, how old are your kids? Are you set on Mama Melrose? (Honestly I never do table-service at DHS. There are so many shows at fixed times that the schedule is challenging enough.)
Finally, how late do you plan to stay in the park? If they add a second Fantasmic, could you do the later show?
Try not to stress. The reason you're planning now is so that everything will go smoothly on the other end. You have plenty of time to work it out. Think happy thoughts. remember - you're going to Disney World!