current info is not to give a fully wholegrain diet till the age of 5. You can give a mix of white, wholegrain though.
From babycentre:
A high-fibre diet is not suitable for babies or young children. Occasional use of wholemeal bread, pasta and grains is fine, but too many of them could fill up your child's tummy, not allowing room for other foods. Do not add bran to your baby's food since it prevents some important minerals from being absorbed. Do offer your child a variety of starchy foods, including wholegrain varieties, but don't use wholegrain foods exclusively until your child is five years old.
From Food Standards Agency:
But if you tend to eat high fibre foods, remember that young children's stomachs can't cope with foods such as wholemeal pasta and brown rice. Also, too much fibre can sometimes reduce the amount of minerals they can absorb, such as calcium and iron.
By the time they're five years old, young children should be eating family food, which is more bulky as it contains lots of starchy foods and plenty of fruit and vegetables. But make sure it doesn't contain too much saturated fat, which is found in butter, hard-fat spreads, cheese, fatty meat and meat products, biscuits, pastry and cakes