And there is a real issue of allowing electric irons in the staterooms. The fire risk is too high for them to take it. And no matter how much some one can go and say 'no, not me', it can happen. There is also the issue of just causing damage to the stateroom. Our last cruise there was a nice, neat triangular shaped scorch on the counter in the bathroom. :/
And, honestly, you have other options.
The irons offered for free are good, also they do have fast, efficient laundry/drycleaning services onboard that will do press only if you really need it done.
Also there are two other things to consider, one, you are on vacation, let the housework stay at home. Second, the other real fact is noone is going to notice a wrinkle unless you've rolled it up in a ball or something where it is one big wrinkle. You'd be better off getting a good garment bag to pack the wrinklables in.