Wailea is a lovely end of Maui and we have always liked the Wailea Beach (it was a Westin the first time we went!). It has an old Hawaii feel without the glitz. Very nice patio for outdoor dining - used to have buffets out there. It would be my choice for a luau (our favorite of several we have been to). They have it on the beach and it has a lot of atmosphere.
You did the right thing in Oahu. Eat also at Roy's. We had a Sam Choy breakfast at the PIP and loved it. Drive to north shore near the Hilton Turtle Bay for terrific beaches and more wide open spaces than anywhere else you will go.
We stayed at the Maui Marriott when it first opened and it has no character but we also got it cheap! Go to Hyatt's Swan Court for its breakfast buffet (daily). Ambiance and great food. You can walk there. The Asian art is amazing along with the gardens. Have the lunch buffet at Kapalua. Enjoy Lahaina! Be daring and drive at least one forbidden road!!!
My oldest daughter and family really liked the bike ride down Haleakala (sp??) in the morning.