Re: 16 month old in body cast
My daughter had a full leg cast. All the way up to her hip at 15 months old. She was walking in it within a week.
She could not use cloth diapers because they were too thick to fit comfortably.
I bought those cheap fuzzy slipper socks from Walgreens. (the adult ones) and cut the toes out, then used that to slip over her cast to keep it from rubbing on everything.
Bathing was NOT fun. It seemed like years of bathing her on the kitchen counter. I washed her hair in the kitchen sink, and then sponge bathed her the rest of the way.
The carseat was even less fun. I have no idea how that will work for you.
Booser seats and high chairs no longer work, because the weight of the cast is too much, and hurts them...so, you have to come up with ways to have them sit with their cast resting on something instead of pulling down.