While you cannot stop visitors from paying attention to the baby you could try to encourage them to include your older child in their praise. The older child should be involved as much as they want and is practicable. Some older children do not want to be too involved with helping care for the baby and they should not be forced to. Also be careful not to try to include them too much in staring at and cooing at baby. If forced to do this it may turn them off baby altogether and increase the jealous feelings they naturally feel towards the new arrival.
Many young children start to act quite babyish when the baby comes into the house.
This is called regression and many children will regress at times of stress. Because many parents are caught up with the new baby they can get irritated with these behaviours and maybe tell their older child that they would expect they should act their age . This kind of reaction can make the situation worse and add to the stress their older child is already experiencing. Most experts and parents would agree that the best way to handle these regressive behaviours would be to expect them and be sympathetic to the child who is displaying them. As small babies sleep a lot, there will be time for individual attention for your older child.