I only have experience with MVC, HGV, and DVC. My 'in general' advice is that timeshares are not for everyone and in particular you have to be willing and able to plan and reserve vacations long in advance when the ability to book opens - 12 and 9 months with HGV, 13/12 with MVC, and 11/7 with DVC. And that MVC resale weeks are the least expensive, HGV is the easiest to use as long as you are happy with their primary destinations and not their affiliates, and DVC is for staying at DVC resorts.
I don't know where you like to vacation other than Hawaii. On O'ahu, MVC's Ko Olina and Aulani are right next to each other. If you had older kids, my advice would be to stay at Ko Olina and walk over to Aulani for the eats and entertainment. But Aunty's Beach House is supposed to be amazing for the 5-12 set. HGV has many resorts at Hilton Hawaiian Village in Waikiki (and has the Penguin Club for 5-12s), we own at and love the Lagoon Tower.
On the Big Island, both HGV and MVC are in Waikoloa with HGV having a much greater variety of accommodations (and the MVC location is points only). On Maui, HGV's new resort suffers from being across a major highway from the beach while MVC's Maui Ocean Club is quite nice. Lastly, on Kauai only MVC has resorts and Waiohai is our favorite Hawaiian MVC resort. Kauai Beach Club is quite nice with great views and a huge pool complex, but Kauai Lagoons has suffered because of an ownership change on the hotel side of KBC - guests are no longer welcome to use KBC's pool and beach.