Husband's baby mama trying to ruin our honeymoon

I (35f) just married my husband (35m). He has a 6 year old son. He gets his son every other week. This coming week we are supposed to go on our honeymoon but it is his week with his son. His baby mama (22f) agreed to keep their son an extra week. Now she's all of a sudden changed her mind and is saying if he doesn't get their son she will report him fir missing his time with him. I think she's intentionally doing this because her engagement fell through. I'm wanting to reach out to her but my husband is saying not to. We can't go on our honeymoon now if she won't keep him. Before anyone says anything I love my step son and yes i would be upset if this was my bio kid. It seems like she's just trying to be petty.

Edit: I scheduled it the way i did because it's easily for me to get off since right after the holidays everyone has spent their Money. I work in a restaurant. This was the best time. As for his baby Mama's age 16 is age of consent here. The age gap may not be kosher but legally he didn't do anything wrong

@Mommaof4 unfortunately it was a verbal agreement. His mom told him to get stuff in writing but he trusted her.

@Mommaof4 they don't have a history of co-parenting problems. There were issues with her and her parents claiming he "abused" her which he didn't. He told me how she would hurt herself and claim he did it and cops will always believe the woman over the man especially when she was legally a minor. I've also been with him 2 years and he's never touched me. He took his parenting and domestic violence classes and they've work out their custody. All their history is with their relationship. Not their parenting. She's a difficult person who lies and is super petty.