Mmm. Yeah. Sometimes my baby and toddler nap simultaneously. But it's all unique isn't it, I struggle to imagine I have any advice.
Probably 51%+ of the time my 2.75 yr old falls asleep by himself, late in the afternoon, mostly on the couch. 49%- of the time he nurses in the mid-afternoon and falls asleep and I carry him up to the master bedroom and lay him on the bed there. My 1 yr old will nurse to sleep and then I will lay her on the bed in our other bedroom. At 9 months that would have been a floor bed. (Putting them over the sides and down into a pack and play seems more likely to wake them up?) Then I grab a diaper in case the toddler needs changing (so I won't have to go back into that room) and close the door.
Simultaneous naps don't let you get things done, but maybe one thing.
My eldest always napped on my back, my middlest napped on my back maybe 60% of the time. My youngest naps on my back a minority of the time. But it is still the best guarantee of me being able to get things done.
See, I think I gave zero useful advice on how to get the toddler to nap haha.