It is not too hard to keep to one suitcase- I was able to for our 7 night including formalwear. Just make sure that your formalwear is not too poofy- take something that doesn't take up so much room and then I just took a pair of black sandals that I could wear with all the formal outfits- that way you cut back on how many shoes you have to bring. Also, bring things that mix and match and you will never use as much as you think you will so keep it to the minimum and you can always do laundry if you need to- we did not have to. Just my suggestions. Also, if you don't want to dress up for dinners you can always eat up on deck in casual wear- just let your servers know that you won't be there for the following meal. But in the end, its your cruise so do whatever you want to and what fits your family best!!