Going to Maui for the first time!
The best restaurant we've been to in Maui is Hali'imaile General Store, which is not all that far to drive from Maalaea Bay. Beverly Gannon is a celebrity chef with several great cookbooks, check it out and enjoy. I'm definitely jealous!
A search for "Maui" will bring up lots of information. That said, the recommendations for the Hali'imaile General Store are right on target. IMHO it's the best chow on the island.
And since you're going to be in Ma'alea, you'll want to check out Seascape restaurant for lunch with a great view of the harbor--it's in the same center as the aquarium. (You are going to the aquarium, right?) Also, Waterfront restaurant is very good.
Our favorite when we go to Maui is David Paul's Lahaina Grill (we just returned last month) - they just renamed the restaurant Lahaina Grill (David Paul no longer) but owners and divine food are the same.
You can make reservations online, www.lahaingrill.com -- we have eaten there at least 10 times -- kid friendly, pricey but about same as Bev Gannon's...great wine list
Assuming you are still here, Kihei's Izakaya Matsu in the Azeka Place strip mall is high quality Japanese at a good value. The menu includes an extensive cooked food selection, including a bunch of noodle dishes. My 8 year-old was slurping down the Zaru Soba (chilled buckwheat noodles) and sampling all our small plates tonight. The bill was less than we spend at our local sushi place in Northern Virginia and the quality is better at Izakaya Matsu.
If Izakaya Matsu was as close to our non-vacation home, we'd be eating there several times a month.
For a splurge, Mama's Fish House is on a picture-perfect cove and the food is focused on locally grown, carefully prepared dishes. It is expensive---we dropped over $120 on an alcohol-free lunch for the 3 of us, but it is worth a visit. Your kids will enjoy the parrots at the entrance and tide pooling after the meal.