Grand Canyon North Rim Activities?

Wife and I are going down to camp on the GC North Rim, and ride the North Rim trail for a couple of days in 2 weeks. Are there any other activities to do in the near vicinity?

We were planning on riding 1/2 day on day 1, 1/2 day on day 2. Was just looking for other possible activities in the area to spend the other 1/2 days.

I know there are GC canyon overlooks on the North rim, but figure we'll be biking the MTB trail along there that will do the same thing, anyway.

Thanks in advance.