Becky, if you can't find anyone with whom to dive, don't give up on shore diving. There are a bunch of pretty benign but fun sites you can easily do. There is a book called "Maui Shore dives" or something similar, which is an excellent reference, and there's also some good information at
THIS website.
You want to shore dive in the morning, before the winds come up, because the water will be calmer. If the surf is up, the visibility on the shore dives (which tend to be shallow) will be poor. If the weather conditions are normal, the viz will be excellent, and you can generally navigate along the reef. The shore diving can be fantastic, particularly if you go slowly. We have seen turtles and sharks, as well as many reef fish, morays, and less commonly seen things like hermit crabs, by shore diving even fairly shallow sites.
If you can find someone to go with, be sure to do the Mala Pier site! That's my favorite shore dive on Maui so far. Very shallow (about 25 feet) and lots of structure which gives shelter to big schools of fish. We've seen white tipped reef sharks, turtles, and gorgeous nudibranchs there. The "legal" entry is a bit of a chore, as you have to wade through coral heads, which is why I would say it would be best to go with someone local, but you could do it by yourselves if the conditions are favorable.
We go to Maui a lot (my in-laws live there) and we have almost given up going out on the boats, because the shore diving is so easy, so accessible, so much less expensive, and you see many of the same animals you do on the charters.
Have fun with the trip!
