Welcome to the world of cruising with baby.
RCI's policy is no discounts for infants. If you pre-pay gratuities then they will charge you for the set amounts which are not age-based. If you pay them in cash while aboard then you can customize the amount. Infants may not be using all the facilities but they do add to the work load of your cabin and dining room staffs. I've seen more than one waiter take a screaming baby away to comfort them while mom and dad scarf down dinner in relative peace. Similarly, your cabin attendant has to handle the dirty diapers and also putting a crib up should you request one.
The cruise line does not provide baby food or formula. However RCI will sell you some. They offer Gerber's organic baby food, as well as diapers, wipes, and lotions, in their Babies 2 Go
program. You order what you want before the cruise starts and it will be in your cabin when you board.