Should my son have the same Apple ID as I do

He should have his own. Otherwise, you will be deleting each others contacts.

You can share the iTunes and App store apple ID, but use separate id's for imessage icloud, and facetime.

Also, take a look at parental controls:

iOS Restrictions:

http://support.apple.com/kb/HT4213

iTunes: Parental Controls:

http://support.apple.com/kb/HT1904

Mac App Store Parental Controls:

http://support.apple.com/kb/PH11496

Mac OS X: Parental Controls (video)

http://support.apple.com/kb/VI28

He should have his own Apple ID and his own separate computer user account if he also uses your computer.