Sorry, I went to Edit the above post and it Timed-Out and would not let me do it so I posted the Edited version below again:
I third the very good one knob(dial) Tesoro Compadre at 2.2 lbs with the hard wired--non changeable 5.75" coil is a drawback. I think the older ones had a 7" coil.
http://www.tesoro.com/product/detectors/compadre/
http://www.tesoro.com/info/fieldtests/current/compadre/
Then the 2 knob Tesoro Silver Umax at 2.2 lbs with an 8" changeable coil.
Then there is the one knob Fisher 1212-X also but I do not know how it compares to the Compadre? I think they quit making them but if you can find a second hand one.
http://www.kellycodetectors.com/fisher/1212.htm
Fisher 1212-X
Sometimes less is more
A Metal detector does not have to be complicated and expensive to be good. You get no extras but a lot of performance features in the 1212-X. Like automatic VLF-ground rejection, variable trash rejection, a built-in speaker and a headphone jack. Just one knob controls the 1212-X. Set the Trash Rejection control and start searching. The 1212-X is a sophisticated instrument that is simple enough for a child to operate. It costs less, but it gives you the same high standard of Fisher quality known worldwide. It is quality you can depend on. Easy to use, beginning metal detector, priced Low, & searches deep!
* Only 2.8 pounds, *with 8" Searchcoil * Cushioned arm rest and foam grip, * Only one 9-volt battery, * Simple, one-knob operation, * Low Price, * 5 year Warranty. Price: $143.95
Also look at the inexpensive Fisher F2 but more complicated and yes the X-Terra 30.
The Minelab Musketeer Advantage is great but the knobs may get confusing and they are not situated in a user friendly spot for the mentally challenged or some elderly people.
Or the Tesoro Cibola
http://www.tesoro.com/product/detectors/cibola/
http://www.tesoro.com/info/fieldtests/current/cibola/
There is nothing from Garrett(forget the Ace 150), Whites(forget the Prisms), or Bounty Hunter(yes there is the Fast Tracker "or" Tacker IV), that I personally would not recommend for your particular situation because simply the Tesoro's are better.
In conclusion IMHO for your particular needs I would buy a Tesoro Silver Umax as the first choice.
http://www.tesoro.com/product/detectors/silvermicromax/
http://www.tesoro.com/info/fieldtests/current/silverumax/
Then the "Cibola" and "Compadre" in that order. The "Cibola" as first choice if you can stand more knobs. As first choice for simple VDI's the "X-Terra 30" and "Fisher F2".