8" Dob sounds like pretty good advise to me. Minutes to set up and use.
Scopes on equatorial mounts can be a bit of a chore to set up and the average twelve year old might lose interest....
Good aperture for the price. Only thing extra you will need is something to collimate the mirrors (align), cheshire or laser collimator. Maybe a red light torch to preserve your night vision and some star charts.
http://www.andysshotglass.com/Collimating.html
http://www.skymaps.com
This comes out every year
http://www.bintel.com.au/Accessories...oductview.aspx
http://www.stellarium.org/
Avoid department store scopes as they tend to be toys....
A couple of places to check out
http://www.bintel.com.au/Telescopes/...oductview.aspx
http://www.andrewscom.com.au/site-co....htm#dobsonian
http://www.andrewscom.com.au/site-co....htm#dobsonian
They usually come with a few eyepieces to get you going.
I'm sure others will chime in with their point of view.
Good Luck!