That all depends on the situation. When my sister was in camp, my parents just took me on a summer vacation. Normally, we all went .. But she was happy at camp so it was fine.
Is it ever ok to go on a family vacation without one kid?
If you have several children and you're excluding one from the vacation event, I would have to say no, unless, of course, there is one heck of a good reason for the exclusion.
This exclusion would be really hurtful for the child, in my opinion, however, you've given no facts, so I can't offer more than that.
If you have only one child, and you wish to have a vacation without the child, that's perfectly fine. There should be times in the marriage where the marriage comes first and the couple has the chance to reconnect and have down-time without the children around.