I'm in the same situation.
A very good friend of my husband is getting married later this year and my DS will be just over 6 months. I asked them what their policy is on children attending and they said DS would be welcome at the church but not at the meal and not at the evening reception.
I wouldn't take him to the church anyway as the last thing I want is him to start causing a scene by crying.
She told me that nearer the time she'd let me know what time the meal/evening reception is taking place so I could arrange childcare 
I accepted what her policy was, said it wasn't a problem but that it meant I would not be attending any of the wedding but of course DH would.
She didn't reply, I don't think she's very impressed.
My DH said I should just turn up for the meal, leave our DS in the car park with someone to watch him (the wedding is a good journey away so I couldn't just leave him at someone else's house) and then once I've eaten go home again without waiting for the speeches. Ridiculous I know 
I've told DH I won't be going at all.
He has said he's going to have a word with his friend as he doesn't class a baby as a child and said he won't need a seat at the table or any food etc and would be quite content on my lap. I've told DH to leave it as I fully accept people's rules when it comes to Weddings and children.
You have my sympathy OP
Could you not just go to the ceremony and the wedding breakfast and then go back to your DS i.e miss the evening reception? That way you won't be away from him for too long?