I'm worried that if I go on vacation, I will lose some muscle because I can only do calisthenics. Should I be concerned?

Many of the people I coach come from a background of chronically overtraining. It is amazing how little it takes to maintain.

Most people don't start to lose lean mass until the second week of inactivity, and even just some body weight activity is enough to maintain it. You can do calisthenics and maintain what you have.