OMG I would find another dentist immediately! I would NEVER strap my child down and force them to have a procedure, NEVER. If it means holding off for a few months until you can save up enough for the anestesia (assuming another dentist that you seek for a 2nd opinion agrees that he needs fillings!).
If it were me, and my 2 yr old truly needed fillings, I would sell something, have me or my husband work some extra hours or tell every single person that sends or gives my family Christmas gifts that you want NOTHING other than help with his dental bill.... other materialistic posessions, gifts, eating out, etc would all be on the back burner....
I am certain you could also find another pediatric dentist that would consider a payment plan, but I would most definately get more opinions that this is even necessary, as anesthesia for such a young child isn't a great thing either (but far better than strapping him down and traumatizing him!!!!). Ahhhh, all those poor innocent children going to that dentist! ACK!
BEst wishes....prayers are in order :-)