Thats a wheelie rider~ for us old kids
If you want to see the grandkids faces light-up (he-he...), show them a wheelie and then a stoppie.
For starters, use platform pedals. Pick a happy medium to lowerish gear, put some leg into it and then pull up on the bars, a finger on the rear brake lever as a drag. Go to the point of feeling you're going over backwards and then feather the rear brake. By braking, the momentum will transfer the balance to forward and down.
Stoppies are a little crazier than a wheelie and demand some confidence. Its all a matter of feel and firm front brake modulation.