I invited my boss and the one coworker who I actually hang out with outside of work. If you are planning to have an AHR, just let your coworkers know they will be invited to that. I'm not having one, but once I let coworkers know it was going to be a small wedding in Mexico, I don't think any of them are expecting an invite. If you have a friendship with your boss, I definitely think she will appreciate the gesture, even if she can't make it.