Visitation question..

Well, my bf now has his visits supposedly nailed down..she can't keep the kids from him. This end of things is a bit new to me so I have a question:

He was about a half hour late returning the kids on Tuesday. He had picked them up because we had a late inspection and were running behind. She WAS not even home but was calling the house at 8pm sharp and when the kids didn't answer she was hot.

He went to the house today and "she "  had told the kids that since he was late returning them that he couldn't get them until 4:30 today. So he sat in the driveway until 4:30 and then left.

Now...I know he shouldn't have taken them back late. It really was a misunderstanding that I told him should not happen again.( The kids had a paper from her  that said he had them 4 hours and since he didn't pick them up til late he assumed he had them 4 hours..) I know ..assuming makes and ass out of you and me..lol.

And again tonight, he was 15 minutes late. The kids couldn't find the key to get inside to answer her call to the house phone til 8:25 .When his oldest son got into the house and called her back she was yelling ...again...and he told her I can't wait til I am 18. I am out of here~ So  now she says he can't get them til 4:30 on Tuesday.

It's not like she is sitting there waiting for them , she is not even freakin home! It 's not like he is an hour late...it hasn't even been a half hour ..and tonight it was 15 mins!

But- I need some experienced friends to advise...Can she do that? How late is late? Please advise asap . I need to know if this is something that the lawyers will have to deal with AGAIN!