Ron:
I think it's really going to depend on their personalities. And BTW, I'm not sure if anyone said this before in your post about staying on-site, but with a 6yo and 2/3yo, you REALLY need to be on-site. Having the option of being back at the resort in 45 mintues could very well be a life-saver, if not at least a sanity saver. In fact, I think that you're going to be better off by doing this every day.
Be prepared to "read" each kid. Don't let them dictate enything by whining to get their way, but at the same time, try to anticipate any meltdowns they might have and try to get them to a quieter place: either back to the resort or a quiet show (Hall of Presidents, American Adventure are two great examples of places where you can nap without leaving the park.
)