train reservations for Golden Week

My son and I will be visiting Japan for 2 weeks around the Golden week. We may be travelling from Tokyo to Kiso Valley, Takayama, Nara, Koyasan and Kyoto.
1. Do we have to make reservations for the trains before we go there? How?
2. The travelling will be within 8 days. Will a Rail Pass be worthwile?
3. Does our journey sounds all right?
Thanks! Jantje

1. Do we have to make reservations for the trains before we go there?

No. Almost all trains have unreserved seating, which can be used without seat reservations. However, considering that it is a busy travel season, I recommend to try to make seat reservations. You can make seat reservations at railway stations:
http://www.japan-guide.com/e/e2016.html

The travelling will be within 8 days. Will a Rail Pass be worthwile?

A 7-day pass is likely to cost almost the same as regular tickets for JR trains. Therefore, I would consider buying one. Note that transportation to Koyasan is not covered by the Japan Rail Pass.

3. Does our journey sounds all right?

Yes, busy but all right if you like a fast pace of travel.

Thank you Uji!!! We don't like to hurry but I didn't know what to leave out of the plan.. My son is 15 and he likes to have time in Tokyo. But also would we like to see some more rural, less modern Japan. Also we are interested in Buddhism. We would like to get the feel more than hurry from temple to temple..
We were thinking of:
april
26, 27, 28 Tokyo
29 to Kisovalley
30 Kisovalley (walking Nakasendo trail)
mai
1 to Takayama
2 Takayama
3 to Koyasan
4 Koyasan
5 to Nara (visit) and to Kyoto
6 Kyoto
7 back to Tokyo
8 Tokyo
9 early flight from Tokyo
What do you think of this?
Too much hurry?
Then what should we leave out?
Many thanks, Jantje

Unless you know Kyoto well already from previous visits, I recommend to spend more time in Kyoto at the cost of other destinations. Otherwise, it looks now like a more enjoyable itinerary. Still not a very slow pace, but well doable without hurrying too much.