Just bought the OTC 2-ton aluminum jack myself from Amazon (
http://www.amazon.com/OTC-1532-Capacity-...B000XSCEBM). I'm impressed with the heavy duty build quality and it has 3 1/2" clearance - plenty to get under my M030 car which is lowered all the way. It also comes with a lifetime warranty.
As many say and it can't be stressed enough - NEVER work under the car using the jack alone. ALWAYS put jack stands in place. A very important lesson to teach your son for his oil changes.
I had a cheap craftsman jack that had 5" of clearance and would just barely not fit under. The craftsman aluminum jacks get terrible reviews on their website...
Whatever you do - I would highly advise getting an aluminum jack as some of those other low profile jacks weight 90+ lbs (versus the ~45-50lbs of aluminum)!