Personally, if the telethon is to be only two hours, it should air on Monday evening of Labor Day weekend, since a lot more people will be home than on Sunday evening.
Besides the fact that people will be home from their Labor Day weekend activities, in most areas, the day after Labor Day is also the start of the new K-12 school year. Thus, parents will be home from their Labor Day travels in plenty of time to tuck the kids away to make sure they have a good sleep before they send their little ones off for the first day of school next morning and then watch the rest of the telethon.
If the telethon can't go back to it's old 21-hour format, I would prefer it going for four hours on Monday (Labor Day) evening from 8 P.M. to 12 Midnight EDT, live in all time zones.
Even if it goes back to the traditional 21-hour format, perhaps it could run from 12 Midnight EDT Sunday through 9 P.M. EDT Monday (instead of the traditional 9 P.M. EDT Sunday through 6 P.M. EDT Monday), again to catch people coming home from their Labor Day weekend activities.
Even an expansion to four hours could allow for plenty of "A-List" stars without having to resort to "B-List", "C-List" or "Z-List" stars.