Getting a child started with bridge

This may be a mishap, but I have started to teach my 9-year old bidding (we play a variation of whist at home already, so he's familiar with card-play) and this is a simplified bridge bidding system for beginners that I came up with.  It is based on 5-card majors and weak 2s (unlike classic Goren)  but has no artificial bids other than 2C.  The idea is to get to a decent contract in a total of 3 bids.

Comments on the bidding system are welcome.

p.s. In case you are curious, the variation of whist that we play with 3 players is as follows:

1. Deal out the cards in 4 stacks.
2. Everyone calls out their point count.
3. Whoever has the highest point count is declarer.
4. The 4th stack (remember that we play with 3 players) is dummy.
5. Declarer chooses a trump or no-trump.
6. I specify the level of the contract.  If they have 20 points, they have to make 8 tricks in a trump contract or 7 tricks in a no-trump contract. And one more trick for every 3 points above it (so 26 points would be 10 tricks if there is a trump or 9 tricks if there is no trump).
7. We lead and we play out the hand.  Declarer wins the hand if they make the level they "ought" to make. Defenders win if declarer doesn't.