I have four boys 10 and under, and have used the H17 for years with good success. (My five year old is the most enthusiastic!)
Selling points for the H17:
"One sail, one kid": In parenting, as in sailing, managing one is easy and fun, two or more leaves less mental bandwidth for not only safety, but also just keeping things fun, and being a good teacher.
Wings: they provide a nice kid-overboard barrier, and more leverage on the sail when the wind picks up. In addition the kids feel more protected or enclosed with the wings. The comfort and variety of seating options they provide is also a benefit.
Trapping is a little more fun and adventurous from a wing than from a hull (personal opinion)
My seven year old can rig it (needs a cleated pull-handle for the halyard)
Buoyancy sufficient for a Dad and three (young) kids (never tried it, but have had another 180lb adult out on mine)
H17 Negatives:
Difficult tacking; learn all the tacking tricks before taking your kid out; you need to be able to quickly return to the spot where they fell off! Easy to do, but you do need to get the procedure nailed down in advance of a kid over-board. This is just wise sailing; H17 or otherwise.
Low boom; it gets a little crowded under the boom during a tack, but once you have gotten the routine down, it's a snap.
Difficult to right if you weight under about 190; However A calm 180lb dad and kid can do it pretty easily depending on conditions.
Advice: I strongly urge you to get the key-hole harness system for your kids;
much safer than the hook.
Here are some images I Shanghai'd from a web-site:
http://www.ps2000.ca/estore/trapeze.htm
I ordered mine from Surf City Catamarans in Santa Cruz, CA.
Peace
Dan
2003 H17
Campbell, CA