Just a thought - although the outfits you described for your children will be fine. Prior to our last cruise I bought my son a kid's tuxedo for about $40, inluding shirt, tie and cummerbund. He was 5 and caused quite a sensation in his outfit (his 6 year old sister was kinda jealous!). The best part was how our family photos turned out on the formal nights - so great to see my little man in a tux! We bought several pictures and used one photo for our holiday cards.