H.B.
My twin boys took three "shorter" naps for quite some time-- they were over a year old before the switched to only two naps. Unless you have to leave the house for work or something equally necessary, I would strongly recommend you just continue working with their schedule. You will have a much happier family if the children are able to nap when they need to nap (not necessarily when you want them to nap!).
This will go by more quickly than you think. Try to hang in there.