Help/Advice someone!!

Hey Group,

I apologize in advance for ranting but I need a little help here. My boyfriend and I been together few years. We are in the process of getting a apartment. We moved out our old apartment 3 months ago and been at a hotel until we found one. He has children. 3 of them. The kids have been staying with his family, along with the kids mother as well. They have joint custody etc and she had wanted the kids near that area. Okay.. The kids mom has been back and forth with guys and such within the past 2 years. She is now in a relationship. With a guy thats in another state like 14 hours away. Video chat etc. Shes 22 hes 19. He came all the way to see her today.. She only saw him on video been dating online 8 months. She told my boyfriend family tonight an hour before her out of state boyfriend arrived that hes coming to see her and shes getting a motel with him, and the kids. Never even met this guy in person before! My bf dad called him to tell him he was pissed the fact his kids going around a stranger I would have been too!!! So she says well if they cant go etc that she gonna leave the kids with his dad. His dad tells her that she needs to be back in the morning and etc to put the kids on the bus. She said she won’t be back till FRIDAY!!! And got in the car shortly after and left! she already has CPS ON “her”. Someone called a couple weeks ago... she seems like she’s throwing the kids off for this guy etc. My boyfriend is considering he can report her to the cps worker about what she did tonight.. hes also wondering if he should fight for full custody of the kids. I think they deserve better parenting than they get with her. What should he do????