[Rich Ives]

In FED (High School) rules the play calls itself, even if the umpire forgets. The runners are expected to know the situation, so any other outs stand.

In OBR (Official Baseball Rules) and NCAA, the umpire has to call it, but the official interpretations say to "fix it" and under no circumstances allow a double play if they forgot. As almost all youth ball is played under OBR, you should have used this approach.