The baby will most likely fall right to sleep after his shots. Give him Tylenol beforehand and your doctor will probably tell you to give him Tylenol for about two days.
My son would eat less because he wanted to sleep all the time. Don't worry if he isn't drinking as much, as long as he's having wet diapers and his mouth isn't dry he's doing good :)
You can give him Tylenol dosage by his weight beforehand which will keep his fever down. He will have a fever probably, his legs will be sore and he will sleep a lot.