tricky!
mine started skipping naps at 2 and 3/4 and it was a hit and miss thing for months - some days if they had a late night or an early morning or run around they would sleep or fall asleep in the car, other times, not.
it would go from 7 naps to 5 naps : 2 up, then 3 naps : 4 up - you get the gist.
the 2 oldest did this, dropped naps completely by 3.5y
I was quite annoyed at first, but then realized it's better to play it by ear. transition periods like this are always difficult - best to observe then force, I think.
I always prefer organized chaos to strict routines that fail, it suits me better to let go of some things and be relaxed.
and that comes from someone who actually hates change, and it is a struggle for me too to let go, but practicality wins me over.
if it doesn't work, leave it.
make a list if things you could do if he unexpectedly falls asleep.
I'd rather give him and early dinner & bath and keep him awake till 6.30pm, then he can go to bed.
or go for a drive after lunch if you can, a 20- 30 mins nap is all he seems to need!
is this helpful?