Hi
Can't speak from experience, but I looked it up in one of my sleep books for you -
For your LOs age - say's nap typically starts 1.00pm (+ or - 30min) w/ an am wake up anywhere from 6.00-7.30.
And bedtime from 7.00-8.00pm.
So if it was me, I would push them back as you were thinking.
Let us know how it goes. Good luck!