Yay for Dads!
I am 30 years old and have fond memories of my dad helping us (me and my 2 siblings) craft Halloween costumes when we were little -- and now that I am all grown up with crazy crafting skills of my own, we're teaming up on an armor / weapons build with me doing armor and him doing weapons. This is particularly meaningful to me because I've never been close to my dad and these last few years our relationship has been much richer for our shared hobby of video games [and now, apparently, Halo costumes).
These really are the memories your kids will carry with them for life.
And a quick technique question - what do you use to prime the foam before you paint it? You got a really great, smooth finish.