Have posted here recently about my ex and his partner and them being very controlling and being mean about me to the kids and basicallly using them as a way of getting at me 
DS1 really likes this girl. He is 13. She is having a party on the night he normally goes to his dads. His dad lives very local. DS1 has asked his dad if he could please go to this party for a bit and be collected at 7.
Ex has some friends staying (who were our best friends when we were married and who I no longer have any contact with). They have not seen any of the kids in 4 or 5 years or had any contact (or bothererd to try since they moved away). Kids do not really know who they are Ex told DD that they have to come this night as it is the only night they have free (they are on holiday here from where they live).
Ex has told DS that he can't go to the party as these friends have come to see the kids espeacially (making DS1 feel bad) and that he will have had several drinks by 7pm and will be unable to drive and pick him up
.DS1 has been in floods of tears and is desparate to go to this party.
I have said I will cancel my plans and pick him up if he really wants to go and drop him over to his dads.
His dad has texted him saying there will be consequences if he chooses not to go and that if he goes to the party he then can not go to his house later and he has to stay here with me.
DS1 now questioning me as to whether his dad has an alcohol problem becasue he is saying he will be drunk before 7pm (he doesn't), saying he thinks his dad is really selfigh and that he doesn't want to bother seeing him anymore 
AIBU or is he being really really awkward and making this really difficult for DS1 (and me)?!