The more you drive, the more confident you will become. In the eyes of the DVLA you are a safe & responsible driver (you wouldn't have passed otherwise!) so I don't see why you should wait. If you don't feel confident enough right now to drive with your DD, then wait until you do, but that is a personal decision rather than one that someone else can put a timeframe on.
I did straight away because I had to. DD1 was nearly 1 then, and I had to drive her older brother to school. I did feel insecure at first, but was super-careful, and it was fine. I tried to plan and visualise the route in my head first before getting in the car, and that helped a lot.
Got into the habit of giving DD1 a snack in the car, so she doesn't distract me. A year later, as soon as she sat in her car seat, she'd announce "I'm hungry!"