I go to Maui often. I sometimes stay in Kehei and sometimes near Lahania.
My favorite spot on Maui is the Ka'anahali Beach Resort. It's very old Hawaiian. The beach is right there, snorkeling at Black Rock right there. Nice restaurant, bar, every night there's live music, walking distance to Whaler's Village. It's not fancy but you will leave very relaxed. They give you a welcome breakfast where you can sign up for all the fun stuff; snorkeling boat trips, dinner cruises, etc. all at the best prices. If you go there, pay for the valet parking. So easy to just walk out and they fetch your car and it's only about $2 a day more than regular parking. There are a few golf courses right there too. Even if you don't golf, you will find them nice to walk on in the evenings.
There are lots of hidden beaches on Maui. Get a book to tell you where. Mostly on dead end streets in neighborhoods. There will be a gate between two houses. Signs will say Beach Access but are small, you have to look.
Hana is o.k. if you've never been, but I have a friend who has a house there. I hire a helicopter to take us. Lands on their back yard and picks us up in a few days for about $200. Cheaper than a hotel! Ha!
Make dinner reservations at Mama's Fish House if you've never been. You'll feel like royalty. Pricey though; dinner for two, with drinks, dessert was about $300. A special treat for us, but we are so glad we did it.
Upcountry is Cowboy Town and lots of little shops and businesses. Drive around the North end all the way. Beautiful turnouts and views. Takes all day.
The volcano is also pretty neat to see at least once.
We book our trips through Costco. Air, hotel, car for around $2500 for two for 10 days.