Kayak, that allows you to search and then compare sites for the best deal. Just for curiosity I did a search for a week in May from Vancouver BC to Maui and saw return flights under 500 per person including all taxes. From other points in the US they are even cheaper and you can fly to Honolulu for around $350 return.
If you combine a cheap flight with accommodation in one of the many Maui Vacation Rentals, you and your family will enjoy a very affordable Hawaii Spring or Summer holiday. There is a complex called Kihei Garden Estates in central Kihei, which I highly recommend for its great location just steps from the beach. You can also walk to Times Market, Longs, many boutique shops and a wide variety of restaurants. The Maui Garden House is one of the two bedroom two bath condo in this lovely property. There are also many other Maui Vacation Rentals to choose from, and because Spring and Summer are considered low season, you are bound to get a good deal. So don't waste any time. Book now for a memorable vacation in paradise!!