I teach Baby Boot Camp to expecting and post-partem moms. They get to bring their baby to class in a stroller which helps relieve some of their stress.
It took them 9 months of their body changing for the baby, so yes, start slow and help them know they are doing well even if they do not see the changes right away. So much of it is mental and hormonal. Also, their body may not go back exaclty the way it was. Help them embrace their new mom body.