If it were me, I'd wait a few years. My youngest was about 6 the first time we went and we all had fun.
I think with a 2 and 4 year old, you and your wife will spend more time tending to the children than you will really enjoying the show (and it's too expensive for that

).
With that said, if you don't do Disney often - I'd say go ahead and go because it really is a lot of fun. If you go to Disney regularly or know you're going back in a few years, then I'd wait 'til the kids were a bit older.