Thanks for steering this back, Dave.
As to the original questions:
Any advice on whether we should pack alot of nappies/diapers in advance, will the cabin have a kettle for making bottles.
the baby will need onboard should be brought with you. That includes nappies, bottles, formula (if not nursing), and baby food (as it's not wise to change a baby's diet abruptly). I'd also bring any familiar toys, blankets, teething rings, and anything else that brings the baby comfort. Actually, this last part is applicable to the 2-year-old, also.
Also, as far as nappies, I'd strongly suggest switching to disposables. Bring along scented bags in which to place them before putting them in the trash...this will make life much more pleasant for your cabin steward.
VERY IMPORTANT: Bring any medications such as fever reducers as you will not be able to find these easily, if at all, on the ship or in port.
Dave's answered the kettle question. Still, you can always ask the dining room waiter or assistant waiter to warm up a bottle. I don't know if they will do this, but you never know.
One thing we found helpful for when our son was little was to practice dining out at home, gradually working up to longer meals. (He was 11 months old on his first cruise, 20 months old on his second.) We also ordered him an appetizer such as carrot sticks to be served the same time as our appetizers. Again, this is more applicable to your 2-year-old. It helped tremendously to have his main course brought out at about the same time as ours.
As I think of more, I'll let you know.
What are you doing for shore excursions?