That's a good question. I would definitely tip them for the baby -- the question is whether you tip the same amount as an adult or 1/2 the amount. I guess I'd tip 100% for the waiter since I know that when my son was a baby and cruised, he'd make more mess than adults for the waiter to clean up! ALso, you may have to ask for spec'l requests for the toddler such as pureed vegies, etc.
You could also ask the guest relations desk on your ship for guidelines too.
Luisa Frey Gaynor
Family Cruise Editor
Weve taken our son at 11 mos, 23 mos, and just recently at 35 mos. Each time we have tipped the room attendant, waiter and assistant waiter 100% from him. The room attendants have always been great about emptying the trash more frequently, supplying bags for the nasty diapers, exchanging lifejackets for the right size, removing the items in the fridge so he doesnt eat them (and we get charged), etc. The waiters usually went out of their way to bring my son's food out at just the right times, and often entertained him with origami, napkin folding, peek a boo, etc. As long as they do something for the child, then you should tip something. If they go out of their way, then tip 100%!
I would ( and did) tip full amount to waiter for your toddler. She sits in a high chair and eats and as noted above I am sure she leaves a mess.( all little kids do!)
As for the cabin steward I do think we left a little less then full amount, but more then half, this was years ago so I am not quite sure, I do remember that the baby slept in our bed and I kept the cabin clean so I don't recall the steward having to do that much more for the baby.
Does the cruise line your're going on have written guidelines for this, some do charge 1/2 for small kids, some still ask for full amount.