Why did you agree to letting the kids stay with STBX? Why not let them see her and their aunt for lunch instead of you getting the scraps on your time?
Also, I don't understand why you are building this fort at STBX's. I get that you are selling your place. But I think there are things that you can do with him without going to STBX's place.
Finally, next time, I'd recommend having a plan for when your kids are around. They surely don't want to go sit around their old home that's all packed up in boxes. What special/fun thing can you do with them next time?
