For a baby meal you get one jar of puree something and a jar of pudding something which is not suitable for a 16 month old. The childs meal consists of a hot something (anything from chicken nuggets, pasta, fish fingers with veg), a pudding and extras like a fruit shoot, yogurt, cookie or chocolate and sweets or crisps.
Having said that the last 4 times I have flown in the last 12 months my requested childs meals were no where to be seen so definitely take back up food. If he is OK with some prepacked meals (for older babies) the staff will always heat them up - or simply put them in a bowl of hot water for a bit.