Can you shift by 1-day?
If you shift your return by 1 day and come back on 1/2, you have 3 non-stop flight options, all L fare that take the tickets down to $367 ea A/I:
MCO to MEM 7:30a-8:39a 2h 9m (assuming the g-kids need to be in school, they could make at least half the day with this one)
MCO to MEM 12:10p-1:17p 2h 7m
MCO to MEM 5:35p-6:44p 2h 9m
Otherwise, you're looking at Q fares for $444.