Beep Beep Beep!

Will has taken to reading (or being read to, anyway.)
He will pick up a board book (probably that annoying 'baby animals' book), and walk towards Carly or me, then he will turn around and walk blindly backwards at us. He is intent on sitting on one of our laps... and is making it easier for us by backing into position. I want to teach him to make the 'beep - beep' sound trucks have when they go backwards. Is that wrong?