What's the etiquette on taking a baby to an all ages show?

The types of show I'm used to attending are generally held in much smaller indoor venues, like bars and church basements. So far as the kid is concerned, as long as he's riding in the baby carrier with ear muffs on, I think he'll do just fine. I'm more worried that we'd be crossing some social line with the other concert goers…

My parent friend has a baby and can't really hang with us — should we keep inviting her?

y apartment is not baby proof-able (think huge bookshelves with breakables on uneven flooring) and I have a friend whose child is starting to pull herself up and toddle around. There's no space for a Pack 'N Play or similar item. We see each other a lot outside of my apartment, but I feel bad that I've stopped inviting her over for meals or parties because a baby sitter isn't a financial option.