Not really appropriate for a child's b-party. It might also be down right dangerous. Children running around playing tag you walking with a plate and drink in your hands to your seat, one of the children running around you trips and grabs your dress to break his fall and pulls down your dress and show casing your boobs.
I can see it all happening right in front of me. Just a thought okay, worse case scenario.
It would have been better to post a pic of the dress, it all depends on the cut and styling I think. Maybe wear a shrug or a cardigan with it. I always go by the rule if you are showing off one asset, cover another just to keep it classy :)
I'd have to see the dress itself and perhaps the way it looks on you to form a full opinion. The fact that it's strapless isn't a big deal, but the fact that it's short seems a bit inappropriate. Perhaps you could wear leggings with it.