It's important to remember not to be complacent about where you live. In NZ the anti abortioners were gleeful and saw this as a step in and hope for their own campaign. They won't stop trying. 

I had this happen (smaller, less stressful party), but what got me was not that the child was left but that they didn't check it was ok, give their name or leave a phone number, (Invite had been given to the mum in person, who I knew to say hi to, I introduced myself, she didn't reciprocate but accepted on the spot). The other parents there were as surprised as us.