Tuesdays is ok (as long as it isn't this Tuesday as I am in Santa Barbara right now).
I think 1 or 2 hours would be fine for a time frame. Other groups I have been part of have been 1 hour, but then a lot of people stick around longer.
As far as age, I think it should be open. I don't see any reason to block younger folks. A parent is probably a good idea at least to start with.
If Bookmans doesn't work out, what about a coffee shop? I know the coffee place by my house (unfortunately not centrally located) would be happy to have us.
There is a group that meets there and call it 'Gangplank West'.
Approximately where is this at?
Are you saying there is already a "hackerspace" or similar gearing up? Should we pair with them? Are we to be only oriented to Arduino, or something more general? Or general, with an Arduino flavor?