How to cope with a new partners ex and kids?

I have met a really nice man an we have almost been together now for one year. Before this we were both in a traumatic 9 year relationship with other partners. He has 2 girls from this relationship aged 6 and 8. I am not very good with kids an im trying my hardest but i cant bond with the children. His ex girlfriend is always in the picture constantly ringing even when she knows we are out together trying to have a nice night. I have tried to talk to my partner an ask him to tell her to give us a break somtimes but he wont say anything because he says shes only ringing for the kids. She uses the kids to get her own way by threatening him with not being able to see them anymore. The ex has now also bought a house 10 doors away from my partner. I would like to know if anyone else had this situation before and if they think its worth constantly bein annoyed by the ex or its better to end this relationship even tho hes the most wonderful man ever?