First, to all those listening: Thanks! 
Your kind offers of help and support are much appreciated and the boys enjoy
the comments!

Well it's not over yet, but I'll try not to be annoying with the emails.
Unknown how the dead battery at Fisherman's wharf ended, but they visited
Muir Woods the next day and had more battery problems.
Payson thought it was a bad battery, although it's a 1 month old diehard.
Suggested that they find a sears store and have them test it.(and perhaps do
some other diagnosis)
Well they got stuck at a gas station and had them load test it after a 2
hour charge. They were told that under load it dropped to 8 volts. They
bought a new battery for $150.
Live and learn. They kept the old one to return to sears at some point, and
figure it would make a good spare. I wonder if they don't already have 2
good batteries, and a lurking problem still. Time will tell.

Presently they should be enroute to San Diego! With only 8 days to finish
the trip, I don't think they will be relaxing at the beach.