My family stayed in 150-4 Puamana for a week (Sep-Oct), and overall we enjoyed it! Fantastic views!
We had a 6-year-old and a 3.5-year-old with us, and while this specific property and Puamana aren't the most pre-schooler/toddler-friendly places, it's pretty good.
They had some sand toys, pool noodles, beach chairs, and a set of adult-size snorkel gear in their outside closet, all of which came in handy. The library at Puamana is almost exclusively adult-focused; bring books for the kids! The pools at Puamana have very little shallow area (just some steps and then it drops to 4ft very quickly); the beach isn't suitable for small children due to the high surf.
That said, Baby Beach is less than a 10-minute drive, parking is easy, and it's not too crowded. That was our go-to beach every day that we went - good snorkeling for the adults and kids, water is good for the kids, low surf. We saw sea turtles 2 of the 3 days we were out there, and got great video/photos.
The location is great. My wife and I walked to Lahaina via Front Street one night for dinner, about a 20-minute walk. There is no sidewalk, so it's not the best walk, but there isn't much traffic on the south end of Front, so we were easily able to move to the side. It's also a very short drive to town, and parking wasn't an issue for us at this time of year. It's about a 3-min drive to the grocery and drug stores, similar to closeby restaurants... all very convenient.
The location is great if you're not sure where you're going to spend your time. We spent a morning in Kapalua, saw Haleakala, did the Maui Ocean Center... and felt like we could get around to any place relatively easily. If you're staying only in West Maui, you might consider a resort or someplace even closer to Lahaina, but this place wouldn't be bad. Conversely if "east" Maui is where you want to be (Road to Hana, Haleakala, Kihei, Makena or north shore beaches), then I'd say stay in Kihei or Wailea. If you're not sure, this is a great, central location.
Overall, we were very happy with the unit. The kitchen is well-appointed. I made several meals and cooked breakfast every day. My only complaint was that one of the central AC units failed the week prior, so we were stuck with temp/portable AC units in three rooms. The property manager did warn us about it in advance, so it was only a minor inconvenience. We had to do a little bit of kid-proofing when we arrived, but otherwise, it was fine for the kids.