This.

Actually, although I have little hope for getting my son on the tandem, I'm holding out hope for his two sons, 10 and 5. If I break them in early then they can pedal me around when I'm old and feeble. The 10 y/o is close to tall enough and the 5 y/o would need a kid stoker kit, but might be worthwhile investment. I'd like to get their dad trained as a captain so he can take his the kids out as well.