Planning a family trip

Any tips for planning a vacation? We want to go to Waikiki from Aug 29th-Sep 4th. I wanted to go to Maui but it's much more expensive. Would it make sense to go to Waikiki then just plane hop to Maui then back? We've never planned a vacation before and now is the best time to go before the semester starts back for me on Sept 7th and since our son's first birthday is on Sep 3rd. Which apps do you use to book your flights+hotel. Would it make sense to get a rental car there too or just uber/walk around? Any tips will help.