Frustrated

[handsintheair]

Hi i am very new to the forum. I definitely need some advice.
I have been divorced from the kids father for 10 years now, we have 2 boys a 15 year old and a 17 year old. Our 17 year old goes to highschool in northern louisiana at a gifted school, and our youngest is with me.  Their father and I do not have a custody agreement, (and i am domiciliary parent) we have always been flexible with visitation, the kids would go to his house every other weekend and we work out the holidays, and special events and what not.
Well the kids father is on his 3rd marriage (not that there is anything wrong with that), and well my children do not like the new wife and the wifes' family at all, the kids tell me that they are always being put down by new wifes family, yet i have made them go to see there father on numerous occasions, whether they liked it or not.
Our oldest son who comes home 1 weekend a month, i have an arrangement with another family (his room mates parents, and they go get him and i bring the boys back to school) never wants to see his father, he calls his father and tells his father that he isn't coming because he has been away at school and wants to spend time with friends and girlfriend, and his father is always angry but agrees.  Our younger son is getting frustrated because their father spends absolutely no time with them, from the time he gets to their house, his father is out playing at concerts or practicing for concerts, and on sundays they are in church all day (not that there is anything wrong with that), and i mean from 10 am to 6 pm at night because his father plays music for the church as well.
Ok, so when their SM family has get togethers the kids do not know anything about them until the last minute, and again they do not want to spend any time with her family, now if their fathers family gets together, they are beating each other up trying to get out the door to spend time with them.
I have always pushed for them to go to their fathers house, telling them its not fair and his your father and he loves you very much.
Anyways, my husband and i have a get together every year at easter, i have never had my kids at easter for the past 8 years, i have never batted an eye, never complained. Well the kids wanted to stay with me for easter this year, (on a weekend that the kids are suppose to see dad), they called their dad and told them this as well. Well, he called and said they were having a get together as well. The kids still said they dont' want to go they want to stay home.
Their father told me that since is its on the weekend the kids were to come see him, that i am on the wrong...soooo does that mean on christmas when it is my weekend the kids stay with me i complain and make them stay with me? no i didn't. So, he tells me that since i will NOT ALLOW my kids to come see him (and he only does this when her family has a get together any other time its ok), that the weekend of mothers day (which he usually has them that weekend anyways and i have never ever complained, i just get the kids that sat evening or sunday morning, that he is getting the kids.
Am i doing something wrong? ever since he has gotten married to this wife he only cares when it involves her family.
HELLPP
i have never ever ever stopped my kids from seeing their father, i would never do that, i have never talked down about him or anything. i have always encouraged the relationship, tried to get the kids and their father to talk about their problems, but nothing ever works .