I agree with Sevens: So why exactly is it silly to carry at a kid's birthday party compared to anywhere else? No, what's silly is to pick and choose where you're going to carry based on perceived risk; that shows a fundamental lack of understanding of the whole point of concealed carry.
Let's continue my seatbelt analogy: Say the birthday party is just a few miles away via safe roads. By SaxonPig's reasoning if someone wore a seatbelt on the way to the party that would also be silly. Instead, they should assess each route they take by car and only wear a seatbelt on the more dangerous roads during heavier traffic, because wearing a seatbelt when you're not likely to get into an accident is just silly.
To me, the only time I don't carry is if it's illegal or if it's too technically or socially awkward for me to do so. Carrying in the shower is technically awkward. Carrying at a funeral could be socially awkward if you're worried that with all the people hugging you the wrong person might notice. So if you're worried that the wrong person might discover you're carrying at a kid's birthday party, then I can understand (though that's more of an issue with your carry gun, your holster, and your clothing than anything else). But if you think it's silly to carry at a kid's birthday party just because it's a kid's birthday party then that's just ridiculous.