Mini
"It's obvious their mother has told them not to interact with him. "
I think you need to be a little bit careful of the above statement. It's not obvious at all, it's far more likely that an 11yo and 14yo are:
Embarrassed at the realisation their father is having a sex life
Worried about how this massive change will affect them
Feel like they've been replaced
Jealous of the new baby.
And all this would be perfect normal behaviour if they were full siblings let alone half siblings who are now competing with a baby that gets to live full time with their Father.
They are 11 and 14yo they will form independent opinions and feelings on the new baby without any input from their Mother.
I know it's hard for you too but you are an adult who has made choices in this situation.
They don't have any choice or control. Give them some time to come round. They need to learn to love him, it won't necessarily be instinctive for them.
Remember also that of course to you your baby is the most beautiful precious thing in the world. To a couple of emotional, self involved (and all teenagers are!) teenagers he's an inconvenience and just not that interesting.
Re the noise, staying up a bit later every second weekend isn't going to do the baby any harm (I appreciate it's stressful for you)
Why not get creative? Get your DH to take the older kids to the cinema over the bedtime period? Or send them out to collect a takeaway at that time? Or you sit downstairs with your feet up for a bit while the girls help their Dad with bath time.
Speak to your DH - noisy games are fun but don't schedule them across bedtime.
Ask him to get his kids involved with the baby.
Get him to do settling time (so he's the one invested in keeping the house quiet)
Putting the girls out the house is absolutely not the solution to this if you want your son to have a relationship with his big sisters.

