If it's a life event they'd work with you. For a vacation, it's probably just going to be up to your seniority and swapping reserve days or trips as appropriate. I'm no at 9E anymore but contrary to allusions, I would not call in sick to go on a vacation, and especially not while you're on probation. I imagine you have a fair shot of making it work, but you might need to offer some money to someone to pick up work days from you if you can't hold the schedule otherwise.