If I were doing that amount of time in Maui, I would do 6 days each in Wailea/Makena and Ka'anapali/Kapalua plus 2 days, one night in Hana.
Another option to consider is to cut the larger segments to 5 days each and add 2 days/nights in Lanai as well, crossing on the Lanai ferry from Lahaina.
If you've never been to Maui, and don't need your itinerary to be jam-packed with activities, and don't mind some leisurely days around the pool and/or beach, it's NOT too much time, but I wouldn't stay in one place. I'd definitely split the Maui time between West Maui (Ka'anapali environs) and South Maui (Wailea), and I would definitely include at least one of the 2 day excursions, to either Hana or Lanai.
Spending 2 solid weeks in Wailea would involve quite a bit of either driving a long way to stuff that's on Maui but still far away, and/or just lying on the beach for a lot of the time you are there,.