Hard to say about the luau. It is a large luau with a lot of seating & I would imagine
DCL has blocked the lion's share if not all for that night. Luau are not cheap. I've attended the OLL offered and cannot say enough good things about it, especially if you've never done a luau I think it's pretty perfect!

But I know when we are on Maui we pay right at $125/pp and that is with NO transportation. Our cruise in 2015 overnighted on Maui so I booked Feast at Lele myself and had a car rented for our 2 days on Maui. But without an overnight, I personally would pay DCL's price to make doggoned sure I got back to the ship before departure. JMHO.
Feast at Lele, btw, is run by the same great folks that operate Old Lahaina Luau. It is a little more for the grown ups IMO in that there is no Imu ceremony (where the pig is taken out of the pit/Imu oven ), almost no local crafters to watch and/or buy from, etc. And it's table service. But it is also a Polynesian luau as opposed to traditional Hawaiian, so there are dances and food from across Polynesia. Both luau are outstanding IMO. I have done both more than once.