If you're leaning towards polys I'd suggest you go watch some for a half hour or more at a store somewhere. IMO they are pretty cool for 10-15 minutes and when they are being fed, but otherwise they do a lot of sitting around.
Based on what's been stated, I'd go for something that "ooh" and "ahhs" non-fish people, and that makes a good fish for children. My suggestion is a small school of shubunkins.