the children

So I have written about my kids before. I have 3 children that I love more than life. The first 2 are from my previous marriage to a man. I got married when I was young to a boy that I grew up with. He was a decent man, and I'm sure it was hard for him when I finally got the nerve to come out. Anywho that is not the point of this post. My oldest two children go back and forth between our house and their fathers on the weekends. As of late they hate it. they don't want to go but they don't want to hurt their father. i have always told them that if they don't want to go they just have to call and tell him that they aren't coming and I will take it from there. they never call and go to his house each weekend and suffer. Every other week they only spend 1 night. It's these weekends that are the hardest. We usually go for breakfast on the Sundays they are with us, the last couple weeks we have spent breakfast going over all that is wrong at their fathers. I guess I should say that at their fathers they don't have rooms or beds or any kind of privacy. They also never get any alone time with their father. He has sense remarried and has a step son (who they say is mean as a snake) and a new baby with the new wife. They have signed the kids up for a bowling league and this is not something the kids like but must participate in EVERY WEEKEND. Anyway this past Saturday we were running about 5 mins behind to pick them up. the wife's phone rang it was K making sure we didn't forget them, it was 5 mins she was frantic didn't want to stay please get here. it was crazy. We get there they bolt for the car and off we go. Now E was very quiet i kept asking what was wrong with him he said nothing, then out of the blue he says can I cuss. Ummm sure buddy whats up.(he's9) He breaks out with my dads a pussy. ummm ok well that's not really a cuss word but it's not a nice word i said, then he says ok my dads a Fu#$8ng a$$hole. I about chocked on my soda. I was speechless. I said what brought that on and my daughter says and my stepmother is a F&^%ing B(*&^. Wow guys I said whats going on. K says she just hates going and never wants to go back. I tell them we will talk about it later but that they know how much they are loved at home and we will always be there for them. Here is my problem what do I do it's obviously not good for them to keep going there. But how and when do I talk to there father. Do I take him back to court, do I just quit sending them and let him take me back to court. Do I stick with the original plan and make them tell him first, I am so stressed over this i hate to send them, I hate how they are when they come back. It hurts me to think I am making them do something that hurts them. I never once would have dreamed that they would feel this way about their father . Help i need advice.