Hi Julie, welcome to the forum :)
I only go on the European short breaks with JY. In my experience most people wear comfortable casual during the day and then change into something a little smarter in the evenings. If you want to really glam up in the evenings then that will be ok; if you want to stick with jeans and a T-shirt that will also be ok - most fall somewhere in the middle. Cindy's advice about a couple of dresses for the evening is what I would go with - if I was a female of course! :D
There appears to be two schools of thought about whether to go on a weekend first or go straight to a longer holiday. Some say test the water first; others say dive straight in. Both have arguments for and against and I think it depends on your character which you recommend. All I would say is give yourself a set time (say a week) to make a decision then if you really can't decide go with a coin toss.
I'm not sure what reasons you are finding for not going - unless you don't like having a good time and somehow I doubt that:-/
Hope that helps.
Julian