Do you want to do something to enhance the trip? Some ideas for that are:
- make some treats for everyone and package them prettily
- breakfast baskets for everyone's room
- buy a different game for each family, then you can pull one out when you all need a laugh
- more costly - design a top ten list and have T-shirts made for everyone (can use a different color shirt for each family if all the kids are coming too)
Do you want to do something to commemorate the occasion? Some ideas for that are:
- frames (maybe collage types if you are more of a casual family) for everyone, then make a point of taking lots of photos to send afterwards
- making Christmas ornaments following the theme of the get-together (seashells) or something special to your family (games you played as children)
- more costly - find a local pottery place (ideally, where you can paint your own) and make up some popcorn bowls or cake plates with your family names or theme on them
Depending on which idea you pick, I highly recommend getting your kids involved with making it - helps them to feel connected, helps reduce your workload, and really personalizes the gift. What a great way to celebrate family - have fun~