If I had never been to Maui and had only three nights, I would consider staying in the Kaanapali area close to Whaler's Village so that walking to shops and restaurants would be an option in the evening. Perhaps The Whaler if looking at condos. or the Sheraton if looking at resorts? Other nice resort possibilities are the Hyatt and the Westin. The Kaanapali Alii are very nice condos.
I would not miss Haleakala or the Iao Valley. I probably would not try to do the road to Hana this trip. Walking around Lahaina is fun and also the drive up the west Maui coast to see the olivine pools, etc.
I wouldn't go to Hana this trip, will take up too much time. Your college grads will probably love Lahaina, just walk around and shop and "hang-out". It is definitely a cool place.
Look at places and comments on this site for places to stay. I always stay at the Hyatt.
Clean, beautiful pools and grounds, great service.