Your timing is reasonable early, but there is a potential bug. Not insurmountable but something that will slow the departure from Poly. Your family will actually be parking in the MK parking lot and walking to the TTC. The rub is getting out of the MK parking lot. There is an alternate exit open from the lot, but traffic leaving the lot can be a nightmare since we, the runners, will be using the real exit from the lot. I have heard stories about folks getting stuck in the lot for 30 to 45 minutes while traffic is metered out and combined with all the other backups in the Monorail loop resorts. Even with no slowdown, they will only have 40-45 minutes to get to the AK parking and out and up to the park entrance area to see you.
If one of your crew is sharp they can figure your pace from TTC through Poly and decide on the fly. I made a spread sheet for my wife that did something similar to that for her. It's not a tough calculation... Four miles from TTC through to Poly. Assuming constant pace, you will be exiting the AK gate in about the same interval. We use that to allow for ease in the field judgement. If they noted the time you pass Poly then they know what it looks like for AK and can make a field decision after getting free of the MK parking lot.
While the AK parking lot is also encumbered on race day, getting into the lot is not slowed. Getting out can be a bear. The path out is limited to one lane on Osceola through to Buena Vista Dr then forced to exit there. I see traffic really backed up due to traffic control on the surface street in front of the mcD. I wonder if taking Sherberth from Osceola down to 192 then over to Epcot Dr and back up to the parking lot would be quicker.... Guessing that may be an option out.
Anyway, if your crew knows where you will be and when they can adjust on race day and see you as many places as they can. mary has made it from the Poly to AK to Mile 25 once in all these years. Recently, we have just decided it was a little bit of a longshot so she no longer attempts.