Is there a quick easy way to Insert two bars of click track  (after tracking completed) at start of each track  ready for export of tracks to mix engineer?

Assuming that the song doesn't start right away and there is sufficient space I use a hi-hat or something and paste in the count off hits by hand. Not easy but I know no other way. Maybe someone else does.

Slide everything 2 measures over.
Insert a drum synth, and program 2 measures of click (snare clicks, hi-hat, cowbell, whatever).
Then bounce it to a track (or however else you prepare the tracks to be sent to the engineer).
 

1- send the metronome to an AUX track if you need to.
OR
 
2- I typically just insert a drum synth (as you mentioned) and paste 8 hi hats in the PRV.
Then just freeze the track, while its frozen, hold CNTRL and drag it to the track you have assigned for clicks).
 
3- Use the browser (Cakewalk content) and grab a hi hat sound from a groove clip. drag it out 2 bars.
Or paste 8 clicks using cakewalks supplied content hi hat sound. Easy with snap enabled.

Assuming these are audio tracks, midi tracks would be easy just draw 4 notes,, doesn't matter what instrument.. 
Like all things Sonar I can think a lot of ways to do this. 
Here's one. 
Because this is audio you need the count in to match the tempo. 
So you'll need a midi track first  sent to a drum VST and draw the notes in.
Just a short clip.
Now insert an audio track naming it COUNT IN and drag the midi clip to the audio track. 
Melodyn will convert it to audio. 
Now you can browse to your audio folder, find that clip and copy paste it over and over to the start of each track.