Honestly, if you want to do transitions, do it when it's best for you. It will make the parent happy, not inconvenience you and really, the kid won't care. It's a transition either way but we don't give kids enough credit. They will be fine.
If doing half days though, morning only so they can play and be distracted from their morning nap.
I've had young kids have catnaps on the floor in the playroom with kids running around them though lol. Kids adapt! If they need a break, they need a break. A screaming tired kid is no fun so you do what you gotta do!