Quack Quack...

[addie]

If you want H to have D for a certain amount of time i.e every other weekend, then you should see a L about that and have it in the D agreement.
Have you tried asking H a few days in advance to take D before he makes plans? If H does take D and then drops her off at his parents there's really not much you can do. I would feel the same way but it's between H and his parents to work that out.
My H has not spent a single "full" day with S11 since our S. He's spent a couple of hours here and there with him. Really, they're the ones who will eventually regret it when they realize all the lost time they could have been spending with their child.