Half finished with the 2X9 hotrock upgrade
Thanks for the info on bikesmith (crankshortening services).
I used an old XT hub and re-laced the 20" rear wheel and added a Sram 34-11 cassette. I switched out the grip-shift for a Sram X9 trigger shifter and my six year old daughter has little problems down-shifting. Trigger shifters are the way to go....because it's easier to hit one cog at a time. With the grip shift she would shift from the 28 right to the 12 and back again while missing all the cogs in the middle.
The Sram X9 medium cage derailleur works well and I hope it will suck up enough chain when I add a small 22 or 24 tooth front chain ring.
The upgrades are working well for now and we are logging road miles and technical single track. For now, the single-track my daughter is learning on is flat enough to be handled by the 34-11 cassette with the stock 36 front chain ring.