Working with obese clients is not the same as working with overweight or average weight clients
As a trainer please take into consideration that many obese clients cannot lie on the ground, or get down and up from the ground.
Also, anticipate the strength of the father when doing partner work with is younger daughter.
I would incorporate moderate walking patterns and create a circuit workout where they can work together in stations for instance, bicep curls with weights, (many obese clients cannot maneuver resistance bands, their girth sometimes doesn’t allow for it) followed by a step touch series, followed by a tricep extension.
Squats can be tough on knee joints, you can have them stand up and sit back down on chairs,or benches.
Bouncing balls, boxing, dancing, walking on treadmills or the eliptical side by side are great too.