Here's a schedule that takes 12.2828 time units.

Motorcycle 1 takes Alice for 9.7464 time units, deadheads back 1.1414 time units to pick up Bob, and takes Bob 1.3950 time units to the finish line.

Motorcycle 2 takes Bob for 3.8635 time units, deadheads back 1.9318 time units to pick up Carole, takes Carole 3.8586 time units, deadheads back 0.8763 time units to pick up Dylan, and takes Dylan 1.7526 time units to the finish line.

Emma skates the whole way, arrives at time 11.1111, and waits for everybody else (including both motorcyclists) to arrive at time 12.2828.