tell you what, tell her this weekend you've already made plans like I mentioned but she can have them next weekend, I don't think this is unfair at all, you've been away so long and you want to spend time with your kids, you're not being controlling, just tell her you made plans already but that next weekend after this one is free and if she wants to take them for the weekend she can, it's ok to be selfish in alot of situations, not selfish to be punitive to her but selfish to enjoy your family. You were in a warzone for 6+ months and now you're back, something horrible could have happened while you were out there and you may never have seen your family again, you're home now and you want to take in every second of your family because you know what it's like not to get to see them everyday.
Listen after a few weeks or months, if things don't improve, you guys are going to have work out a custody schedule anyways and although it's nothing to look forward to, it's not something to be afraid of either, its the reality of the situation and it's not just reality for you, it's for her too.
