Yes - I was the one & only (?!) bridesmaid to my best friend 10 weeks after giving birth. And same as you, the wedding was 2 hours away, dc was ebf (and first child - so still finding my feet!), etc. etc. I kept trying to drop very unsutle hints about how absent / useless i was going to be during the day (and in the run up the wedding too, come to that - had to miss the hen do was dc was just a few weeks old), but nothing really seemed to sink in....
The upshot was, I ended up wearing a horrid dress that I could just about bf in (& was cheap so I didnt' feel too gulilty about wasting the brides money), I felt incrediable self-concious the whole day about being "on display" (walking up the aisle, photos, sitting at top table etc.), and either my dh or I were absent from the service/reception throughout the day i.e. we "tag-teamed" it. And it was stressful and incrediably hard.
However, my friend & her dh really appreciated us being there, and were understanding that we were doing our best. A wedding should all be about the bride & groom, and however much I didnt' want to do it, I was glad that I made the effort. Although, I definitely wouldn't have done for someone who wasn't such a close friend!
I was recommend that either you or your husband are in the wedding party, as you will need one of you that can take the strain in looking after the dc (e.g. my dh spent the service walk round the block outside the church, then was ready to hand dc over to me straight away afterwards to be bf in the car). Or could you get a parent to come with you to do this?
Also, make it clear to the bride that your priority will be the baby on the day, as you will be a new mum who is breastfeeding, and that you will not be very "useful" as a bridesmaid due to this. If she still wants you to be a bridesmaid, then do it if she's a best friend, or get out of it using the baby as an excuse if she's not - if she doesn't understand - she will as soon as she has her own dcs!