Aerodynamic kid's trailer with suspension
Generalisations on child-carrying trailers


Based on stroller designs, so suspension is rare.
Small wheels on cheaper designs.
Seat is positioned for visibility and for an adult not to stoop too far to attend to the child. This is bad for stability and aerodynamics.
Built like tents: frame with some kind of fabric over it. I've seen trailers/strollers with mesh fronts and ones with rollable plastic fronts, but as the overall shape remains a modified brick with fluttering fabric, I doubt they'll be very aerodynamic. Your velomobile is designed to have a minimised wake, so the trailer gains no aerodynamic advantage from following it.


What I would do: Make my own.


Find a suspended cargo trailer or design and construct one from tubular sections of aluminium or steel.
Create a fibreglass clamshell from scratch using insulation board for the former, like the Kingsbury Quattro
Or find a junk fibreglass boathull, invert it and add a vertical section until the interior height is sufficient. Fit a polycarb window on each side, but your child probably won't appreciate a porthole which shows the rear of your velomobile.
Use good hinges and hydraulic struts to hold the shell open (like a car hatchback)
If the shell needs catches or straps to hold it shut, there should be a release mechanism on the inside.