A.N.
If there were lots of kids - none invited - I would say suck it up and you are being petty,
;-)
But since you are coming a long way he must expect you to bring your two children.
As your husband is the best man he must expect him to bring his wife and family.
He needs to remember your two children.
As you are part of the wedding with your oldest and your youngest is only 14 months he must expect you to bring him too - so you will have two children.
He is being unreasonable. He must expect you to bring your two children.
No question!
It may be an inconvenience to him, but tell him, sweetly, that this is a family celebration and you don't plan to stay home with the baby or split up the family in any way.
Offer to sit at the back during the ceremony or near a door and to take the baby out right away if he becomes fussy or noisy.
Good Luck!