This is your
honeymoon, they shouldn't expect to be invited. It's not like your not inviting them to the wedding, to share your happiness with them! You can always plan something fun to do with them after the honeymoon.
If they are not too excited about even the wedding, I would not invite them to the honeymoon. Your honeymoon is to celebrate your new life together, it's about fun and romance, not about trying to make other people happy. All it take's is one "incident" to put a damper on things. For once it
is all about your guys!
That being said, I'm getting married in Orlando, and then Disneymooning. I have DS's 14 & 18. We are bringing them to Orlando for the wedding, and spending two days at the parks with them...then they are flying home, and the rest of the time will be just for us. My DF was kind of reluctant sharing a honeymoon with the boys, (not because they don't get along, but because it's a
honeymoon!) So we came up with that solution.
There are a lot of people who share their honeymoon with their families, and have a blast...but if you foresee any type of turmoil, or simply just want to be with just each other, it's YOUR honeymoon.