With a 6 am flight you want to be IN the airport at 4am (at least I do). To get there by 4am, what time do you have to be in the car? To get in the car by that time, what time do you have to be loading the car with kids, adults, and baggage? To load it all up, what time do you have to wake up?
Does it really still sound like fun to your husband?
We've done enough of those flights to
Disneyland (same time, around the same landing time)...it's a PAIN. Especially with little kids, no one really sleeps, everyone's excited...and then you're at the park with no room...and you might not enjoy the day as much as you would have enjoyed it, if you came in a bit later.