Bob,
 I've lashed the bikes together & mounted the kids, but i invariably back
over them when parallel parking...
The work around is to pull the middle seats ('93 EV MV) & put the bikes
inside.  Roof racks clamp on, no drilling.  I find that with the proper set
of bungee cords the kids fit on the roof rack and are reasonably happy up
to approx. 65 mph.  Above that they tend to bang on the roof...
Moe