Pirates are easy. Ever see the disney show "Jake and the neverland pirates"? There is a girl names Izzy and she carries Tinkerbells "Pixie dust" around her neck in a pouch! =)
Honestly, I would avoid guns. Just not cool, IMO~
Without seeing the body of your message (about the weaponry) I instantly thought Wizard of Oz, or Harry Potty (but your kids are pretty young for HP characters). I Do soooooo love couple/group costumes!
I used to do daycare for a set of twins and their older sister (2 years older). My hubby always called the twins Thing One and Thing Two (this was years ago prior to the PBS show sort of reviving them). So for halloween one year their mom did that for the 3 of the girls. Older girl was Cat in the Hat (black sweats, tail, she stuffed white adult gloves and made them stay on..and the hat of course, black nose and wiskers)..and the twins were the things..(red sweat suits, circle patches saying thing one, thing 2..and blue wigs she got cheap!) VERY cute and surprising when they showed up at my door along wiht another sib set of daycare kids...baby sister was a lamb and big sis was in an adorable Mary (and her lamb) suit with the frilly bloomers and staff and all!
Have fun!