For a productive photographer, better a well-used workhorse M3 than a mint S2 that should handled very carefully. For sitting on a shelf and looking pretty, a mint S2 would be fine.
The OP stated that he had an S2 and was wondering if he should move to an M3.
OP, down load the M3 manual from the web and look at loading film. Even my old M4-P with it's fast loading take up spool (FOR ME) was not as fast loading as my S2.
Aspheric Leica glass and ZM glass is great if you have the cash. New CV glass for it speed and price is wonderful. Can't get them for the S2 but they fit the M3. Early CV glass is mostly still available new or in great shape at reasonable prices for the S2 as well as the M3.
The M3 does have a single shutter speed dial which is faster. Some people find the M3 rangefinder easier to focus with.
You can get Nikkors in LTM to use on an M3, I had a few and they were great.
Both will serve you and your children well for many years.
B2
Both will serve you well for many years.