Until recently, both DH and I usually go to the kids' parties - because they've been the kids of people that we're both friends with -usually before we all had kids. But, now DS is starting to get invited to parties of preschool friends - and I don't even really know the parents other than "Hi" at dropoff.
The last one was on a weekday afternoon - too early for DH to get home. I actually had NO idea who the kid or the mom was - it was maybe 3 weeks after school started. I emailed the RSVP and told her that DH wouldn't be home, would it be okay to bring my 9-month old? She said, of course, but thanked me for asking. It was at a jumpy place, so clearly, the baby wouldn't be participating, etc. But, I didn't just want to show up with the baby. There were two other moms there with babies too.
So, he got invited to another one. On a weekend. I figure that one of us will stay home with DD. But, when I emailed the response, I said something like "If, for some reason, it doesn't work out that one of us can stay home with her, do you mind if I bring the baby?"
Is that bad to ask? I realize that at some point, she's going to be old enough that, unless she's invited too, she can't tag along, but under a year is okay, right? And asking the mom is good too, right?
Re: Tacky, re preschool parties?
I think it's pretty much a given that younger siblings are fine to tag along to parties. Everytime I've taken my dd to a party with her pre-school friends there are always siblings there. I take my youngest too if it's during the week and I've never asked if it's ok. I think it's nice of you to do so but probably not necessary.
Around here siblings always seem to be welcome!