The newer ships are more impressive, with more activities, however be aware that you will pay 3rd pax price for the 10m old - and that some lines will not babysit him so you are going to be pretty tied to one person always having to be with the child. I wouldn't recomend it.
Check out Independence we did Navigator out of the school holidays and had a few parents with baby's and toddlers with them they provide high chairs and the waiters seemed to look after them?you may get a free space for the baby try different agents,please note there are restrictions regarding the pools with young baby's .
Babysitting - over 1 year only
Adventure Ocean club for 6months up called AquaBabies - one 45min session a day only
On Freedom, Liberty and Independence there is a special Baby Splash Zone pool where they are allowed in in nappies - other ships not allowed in pool in nappies.