Mountain lake, cold water ... wouldn't especially want to take a 6yr old out on either boat, tell the truth. If Tahoe's winds are as gusty and erratic as most alpine lakes, you will
be swimming from time to time. I sail a Bucc18 (18 feet, not 17) at 7300' and it's a freaking handful. Friends sail Hobie 14s & 16s, and they dump them frequently. As in turtle. It is not easy to recover a turtled cat. Kids go hypothermic fast. Here's the reality
of sailing beach cats on mountain lakes with young children.
Hobie16's a bit faster than the Bucc, but not hugely. Tacking a beach cat takes motivated and moderately athletic crew. Bucc is simple to rig, very few strings to pull, can be kept mostly upright with a reefed main and aggressive hiking. It is NOT a sunset cruiser, unless your winds are far more reliable than ours. It ghosts along on very little wind and begins planing in ~8kts true. Above 15kts, it is very difficult to hold down and takes on plenty water. It won't stuff like the H16 & it's easier to depower. Top speed is NOT "5 or 6 mph" -- it's a planing dinghy exactly as fast as the 470 or Lightning or MC Scow, meaning bursts of 11-12kts (and yes, I can document that.)
As for the Bucc seating 4 or 6 people ... maybe on some gentle Ohio lake with steady evening breezes. Don't expect to seat anyone on the low side in a blow; and despite the invitingly long cockpit, be aware the vang, bridled mainsheet, tall CB trunk, and long tiller make it difficult to get people across during maneuvers. I've said it a dozen times: the Bucc18 is a two-up racer with some limited daysailing potential. For where you are and what you want to do, I'd advise a small keelboat like the Potter19 or Venture17. They are just as easy to trailer, rig, and launch, but they have inherent stability the H16 & Bucc18 lack. And a cabin to stash the tyke for nappy-poos.
Also look into the Mariner19
, which straddles the line between dinghy and keelboat better than any craft I've seen. It's a glorious sailer, too
. Flying Scot
is another possibility -- same giddyup hullform as the Bucc, but it is ~350lbs heavier, 80lbs of that in the ballasted CB. That makes a world of difference in stability, with little difference in speed. Try THIS on a Bucc18 ...
... and you'll be pointing your mast at the bottom.