Hawaii honeymoon

Hi,

Here’s my problem:

My future in-laws have a timeshare that we will be using for our honeymoon in Hawaii. As soon as I tell this to travel agents, they say they cannot help me. I need help booking flights, renting a car and planning activities. We are leaving on December 15 and will stay in HI (Maui and Big Island) for 7-10 nights. I would really appreciate some help. Thanks