Oh, I don't have any problems with a 7 speed cassette, but high quality shifters no longer support a 7 speed rear.

All these little bikes need is a one piece drop bar (come with a two piece to support the revo twist shift) and a nice shifter/brake lever.

I plan on a quality groupset for their next bikes, and will just swap frames as they grow.

Since there don't seem to be any quality 7 speed "brifters" I'd be happy trying an 8 speed lever with plans of re-using it, but the options seem very limited.

I don't think I could use anything 9 speed or higher since the cheap cassettes on their tiny bikes would require a "stay-widening" and new hub just to fit a proper cassette.

I have a feeling my best option is to buy cheap Tourney 8 speed "brifters" and let em go when the bikes do.