[BrianR]

Does oral count? Although my answer won't significantly change, the oral part came first. My then-gf was blowing me in my bedroom while our parents were outside at a family BBQ. My mom was sneaking up the stairs, stepped on the creak which I heard. We jumped up, looking for some way to hide a massive boner in three seconds or less. I wound up sitting down again and pulling her (fully dressed) onto my lap.

Mom only saw us fully dressed, giggling like a pair of happy babies, looked at us strangely and told us that the food was ready and to come down. I told her we'd be "right there". (as soon as I put "it" away).