Why not do what I did for my kids. I got a 7'6" 6 wt fiberglass blank (I know noone makes them in 6wt anymore; but the 5 wt is so close it words just as well) and built the rod with a short, rather thin 4" front grip and a thin 2.5" rear "fighting butt". I did this for my daughter so she could cast it 2 handed when she was 6 years old. The rod was passed on to our two boys (there is 8 years between Mel and Derek and another 4 between Derek and Reuben), and her brothers started to use it when they were 5 years old. It worked out very well for the intended purpose and the fuller flexing, more flexible fibergalss blank made it easier for them to feel the rod bend and load.
Unfortunately, the rod got broken by the boys when they had a fight over who would use it when the youngest one was 8. The older one still liked it eventhough he was 12 at the time and had a 9' graphite rod of his own. He thought it was cool to have a small 2-hand rod like Dad's long 2-handers.