My only question would be why the Secret Service allowed the kids to get on the elevator to begin with. I thought it SOP to have an agent at the entrances to elevators.
My guess--and this is only a guess--is that the kids got on the elevator on the last ride before the elevators were shut down & the agents were posted. Doocey had to wait until Kerry got his ride & the USSS released the elevators for normal traffic.
I just can't even begin to imagine the traffic snarls in NYC and Boston during the conventions.