We had two weddings DD was 6 1/2 months at the time (4 1/2 corrected), we were BF'ing and both weddings she went to, one, we didn't take her to the Ceremony and when we got there they asked where she was

But we were worried she might cry during the ceremony and after a cousins baby did it at our wedding and for half the ceremony on the video you can hear DA DA DA DA.... we didn't want to do it to someone else. The other wedding she came to both and was perfect I BF'ed her in the church minutes before the Ceremony, so I knew she had a full belly

When they at that age they usually feed play sleep, DD slept well at both ceremonies and we just made sure she wasn't overstimulated with too much attention

I would explain your situation, we did to one wedding as she wasn't on the invite but they were like oh no that is wonderful, no problems
I hope it works out and you all get to go
xxoo