Hi
What you can do to promote your chances of acceptance is to keep the boy in an adjoining cage with interaction through the grid but no chance for him to getting through them or over them in any way during the op, recovery and the 6 weeks post-op wait. It means that they are familiar with each other and the bonding will hopefully that bit less over the top than a date although brace yourself for some drama when boy meets girls for the first time. The piggies are all at an age where their biological urges are towards accepting each other but there is never a full guarantee for a match.
Your plan B would be in the longer term to find your boy a little wifey of his own and keep your piggies in two cages either next to each other or above each other.
Here is our neutering information pack:
Neutered / De-sexed Boars And Neutering Operations: Myths, Facts and Post-op Care
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
The chapter about mixed pairs applies basically also to a mixed trio. The sows should be good friends; otherwise your boy will in the long term side with one of them and you can end up with an outsider situation. If the girls get on well, then a mixed trio or quartet is great. The other challenges are usually the same.
A Closer Look At Pairs (Boars - Sows - Mixed)
After Tegeirian's sudden loss a few weeks ago I have currently got 5 mixed trios (and one sows-only trio) but sadly no longer a mixed quartet.
My young teenager Baeddan at the height of his hormone output at around 6 months was sadly too pushy with either sow trio he was introduced to and now lives with his 6 weeks older half-sister Blodyn as my plan C. They get on well since she is not dominant.
His litter brother Brangwyn however was happily accepted by his neighbouring middle-aged sow pair who saw him growing up through the bars with a minimum of fuss - this was plan A going off perfectly. The younger of the two sows is a bit of an iffy bonder so little Bran will hopefully see out 3 years old Beti without the need of any more adoptions. Brangwyn is a bit of a teenage pest especially with Begw at times but the bond is stable.
I hope that this will help you. Crucial for a successful neutering operation is to find a good vet and nursing team.