The two nap schedule is very normal and needed for his age. Typically around 18 months - 2 years children drop their need for a second nap and are sufficient with one. Even the early risers. It might be hard to imagine at this point in his life, I know!

If the caregivers are knowledgeable about child development and typical toddler experiences they’ll be empathetic and helpful during his natural adjustment to one nap during the day.

What is his typical home nap schedule?

He’ll probably be exhausted upon starting a program but adjust after a week or so. You could consider slowly stretching his nap to start closer to 1 to help prepare yourself/him/the caregivers. A lot can change with sleep by 18 months.

I’ve worked in daycare and Montessori schools and a late nap isn’t a “Montessori thing,” usually it’s a kids lunch and teacher break schedule thing. Although I’m not sure how much earlier you expect the nap to be?