Loose pedals on Norco MTB Just replaced my pedals on a very old Norco MTB.  

I noticed while working on it that the whole pedal structure is wiggling from side to side is this normal? 

I took the plastic caps off the base to see if it is an easy tightening fix, but not sure if tightening that bolt is the  way to correct the problem?
You have a loose bottom bracket (BB). It needs to be replaced.

You need to buy a new bottom bracket along with two special tools: A crank puller and a bottom-bracket tool.

If your current bottom-bracket is cup-and-cone style (it probably is), it can be removed with basic tools and elbow grease. If it's cartridge style, it can be removed with the BB tool.

Here are links to all three at Amazon:

BB

BB tool

crank puller

Or, you could take the bike to your LBS and have them handle it. This is a common operation and probably wouldn't cost much.

BTW, the bolts that you see underneath the caps hold the cranks onto the bottom bracket spindle.