My 2013 Sprinter Owner Manual says that you don't deactivate the co-driver airbag:
Occupants, in particular children, must sit as
upright as possible, fasten the seat belt
correctly and use a suitable infant restraint
system, child restraint system or booster seat
suitable for the size and weight of the child.
Children can be seriously or even fatally
injured by an air bag deploying. Observe the
following important information if it is
absolutely necessary to carry a child on the
co-driver's seat:
-The co-driver's front air bag is not
deactivated.
-Never secure your child in a rearwardfacing
child restraint system on the codriver's
seat. A child in a rearward-facing
child restraint system on the co-driver's
seat can be seriously injured or even killed
if the co-driver's front air bag deploys. Only
install a rearward-facing child restraint
system on a suitable rear seat.
RWhere permitted by state law, if you secure
your child in a forward-facing child restraint
system on the co-driver's seat, move the
co-driver's seat as far back to the rear as
possible. You must then use an
appropriately sized child restraint system
recommended for the age, size and weight
of the child and secure it with the vehicle
seat belt in accordance with the child seat
manufacturer's instructions
