My daughter will also be attending K1 afternoon class... I am probably going to drop her afternoon nap and move her bedtime up earlier. She's 3 now, and these days if she has a good afternoon nap, its hard to put her to sleep at 8.
Haven't really thought about how to actually do it, although probably when I do drop her nap, I will make sure that the first few days are not too packed with activities that will make her really tired, until she is use to not having a nap.