That routine sounds fine to me - I don't think there's any need to change anything really. If he's had a good breakfast and a snack not eating much after the nap isn't an issue, especially as he is hungry for his dinner. Think of the snack before his nap as an early lunch and whatever he eats after it as the second part of it!
I would just offer food and let him guide you, if he's napping well and sleeping well he's getting enough! My toddlers never ate much at the end of the day, but they ate lunch so it all evens out in the end.
Laura