I would love some advice:

We are about to take a holiday to Hawaii. Usually when we go away I only take a point and shoot camera and have decided this time to take my Canon 60D.
I only use one lens and that is my prime Sigma 30mm f1.4.
The question I have is has anyone ever been away with just one lens either a 28mm ,30mm on a crop body or a 50mm on FF?
I think the trip away would make it a challenge using this lenes.
Then if I do get another lens should it be the cheap but sharp Tammy 17-50 nonvc or something else?

Thanks in advance.