The ship does have a ironing room on each deck, but does not supply an iron in each room. I opted to purchase a travel iron and take it with me. Best idea. No waiting to use the iron. Invest in the travel iron, its worth it.
So far in all the cruises we have taken, our camera etc. has always been fine left in the cabin. We also put money/travelers checks, passports, etc in the safe while cruising too, no need to worry there either.
Something you may want to try while packing, use the plastic dry cleaner bags over all the dresses and suits, sure saves on wrinkles, haven't had to iron anything yet, give it a try, it does work :-)
I am going on Victory on 5/28 (are we excited yet????????) and was researching this question myself:
I emailed Carnival and was told that no Carnival ships provide irons in their cabins. Suggest you pick up a small travel iron, should only be a few $.
As for the safety of personal belongings in the cabins...who can say. Personally, we have done 6 cruises, and left all kinds of things, cameras, jewlery etc around of cabins, and have never had a problem.