I've done exactly this!
MOH at my friends wedding, baby was one week old exactly and I'd had an emergency c section! Baby was overdue too so we were very much winging it with arrival date and how things would be and obviously didn't expect to get my belly chopped about (I'd wanted a Hypnobirthing water birth!)
How we did it was that me, DH and baby went to brides house as normal to get ready in the morning. Meant I could feed whilst having my hair etc done, DH could take baby as needed (my friend didn't care at all about him being there on the periphery), my mate got to have all her BMs there and I didn't miss out.
DH then took baby to ceremony location, and I travelled in the car with Bride. At the ceremony, my parents met my DH and took baby. They were outside with baby for the ceremony (either outside outside as it was nice weather or in a comfy room at the venue). I think it would've been really disruptive to have such a tiny baby in the vows part and it's usually pretty short so baby was fine with parents and fed before I left and after ceremony finished.
After ceremony they were there with baby outside and we and our friends were with them/baby, fed as necessary (bf), close friends had a cuddle and cooed over baby.
Then when it was time for the reception -speeches, meal etc I left baby and parents in the side room and took part in the wedding. Popping back regularly between the different parts. Had a nice glass of fizz and a lovely time.
Then me and DH left part way through the evening do with baby, and parents went home too. By that point I was really tired, mostly because I'd had a week of very little sleep and was still the size of a bus. The EMCS actually was very little of the issue for me personally. But it was totally worth it to see my friend get married.
Clothing wise I had a stretchy wrap dress that was adjustable and I had it altered before and some poppers put in for easy feeding access and so it didn't fall down off my mammoth wangers. I was still huge. I wore breastpads and probably a sanitary pad I imagine and didn't have any issues with leaks from anywhere! 
As far as vaccinations goes, unless you think your child is likely to catch one of the diseases that they get vaccinated against then it makes naff all difference. Vaccinations don't protect against colds! Your baby will catch all sorts of things as they get older irreverent of jabs. Yes new babies might be a bit more fragile but you don't have to do a receiving line with everyone kissing and hugging your baby.
I think for me the biggest issue is if you have the baby with you, even if the baby is in the same room and with your DH but not you, then it's very hard not to be totally focused on the baby and either resent having to be in the wedding and not on the sofa cuddling your baby or just zone out of the wedding and miss it because you're in sleep deprived baby loving dream land. Plus wedding receptions tend to be a bit noisy post speeches and drunken so not especially baby friendly. I can't emphasise enough how helpful it was to have my parents who I trusted completely to be there in the sidelines with me able to go backwards and forwards knowing baby was safe and seconds away but also that in the wedding I could give my focus to my friend on her special day. Baby was in a nice warm quiet location and completely unphased by it all - they slept through most of the day! My friend was totally accommodating and if I'd said I can't come at the last minute or I need to do it like this or that, she would've said absolutely, do what you need to do (it's easier if the bride has kids and understands!)
The rest was the easy bit for me. I'm so glad I was there and no matter how swollen and pregnant I looked in the photos, it worked out just amazingly. And as an added bonus we have some great memories and very sweet pictures of our tiny baby at the wedding with our close friends.
I hope it works out for you as well as it did for us whatever you decide is right for you and your baby
x