You can do 2 things -

1) look at the reward charts for the airlines you have miles with and figure out how many you need for different locations.

2) Then look at those locations and determine what points you have to use for hotels.

This will help you narrow down locations significantly. For example - If you don't have enough points to go to Hawaii you can take that off the list or if there aren't any hotels where you have points for a location you may want to take that location off the list.

I always find this part of the planning the most fun - you get to check out different locales and figure out what works best for you and your family. Good luck!