Barri, sounds like a very fun idea! Sewing with my nieces is always entertaining. So much energy. That said, think about this. I've found with my daughters and nieces the small squares are intimidating. If I were starting from scratch I'd start bigger then maybe the candy size as a second project? One of my favorite easy patterns I did as mystery.
http://www.quiltingboard.com/blocks-...e-t209515.html
This has great nine patches and flying geese. Idk....I bet there are loads of great easy projects. Oh, my daughters liked 2.5" strip quilts and triangles are very popular with them now too.
Keep us posted! Like I said, GREAT niece project! My niece is always sending me pictures of new little quilts she's made. I'm so proud of her. I also just taught my daughter some fm quilting. She may never stitch in the ditch again!