There are a lot of boats in Lahaina Harbor and many good ones. I go out on the Die Hard when I am there. It costs around $200-225 per person if I remember correctly. Boat leaves any time between midnight and 3am so youre out fishing the buoys at daylight. Not sure if thats for you and your group or not but I like it because it puts you fishing at first light which is when we seem to have caught the most fish. You will fish the buoys for a couple hours and then troll back to the harbor with gear. Back early enough to still do something in the afternoon if you want. They are fisherman and are serious about it, so if youre just out for a booze cruise there are other boats around.
Also consider and talk with your group and the boat about seasickness. Unless you stay inside the shelter of Lanai and Kahoolawe on southern Maui, it could get pretty rough. I have been out a few times and its never been calm once you get beyond the shelter of the surrounding islands.
The deal with the boats there is that they keep the fish that are caught, but they will share enough for you and your group to eat for a couple of meals. They have always been generous with sharing and never felt like I didnt get enough to satisfy me.