Pinata Costume - the maker said "I used a glue-gun to cover a tan dress with layers of streamers to make a Piñata costume!" (To make it a couples costume the boy could be a birthday boy or wear a sombrero)
DIY Family or Group Smore’s Costume Tutorial from Cheerios and Lattes. This is one of the best and easiest family costumes I’ve seen. All you need is paint, cardboard, pillows. For more kid friendly Halloween DIYs go here.
Last-Minute Halloween Costume Idea: How to Make a DIY Flower Costume