Firstly which breed is your dog.
Yes you can give cerelac to him and this is the right age to start weaning.
In addition i will advise go for something like lactopet which is designed for dogs at that age.
Also now you can start some premier dog food starter. You must blend the kibble in your food processor or mixer so that you get a powder form of kibble. this mixture is easy to be fed (soaked in warm water). Make this as one or two time diet for him. After 1-2 weeks start giving him soaked kibble.