Actually, modern era is not in general a good choice for limited space and smaller radius curves. The earlier the era, the smaller the rolling stock and locomotives, and the shorter the trains (if you care about being prototypical - it's not a requirement to enjoy the hobby!). The only exception to the rule happened in locomotive size with the switch from steam to diesel. Diesels do look better on sharp curves than later era steam locomotives. But 1st and 2nd generation diesels were considerably smaller than present day diesels.
For small steam, small cars (frieght cars were just reaching 40ft in 1910), and shorter trains, before 1910 is your best bet. However, there's not a lot commercially available. Early diesels is your next best bet (F's, early GP's, SW's and their non-EMD equivalents) because car and train lengths really started to grow in the '60s. In the '50s, 40ft cars still dominated. Engines had 1500-1800 HP instead of todays 3600+ HP.
However, the issue of era is mostly personal choice (if you even pick an era). Your boys may have particular desires to see very modern equipment, but then again they may be happy with an older era, too. There are quite a few of us who happily model eras we never saw in real life.
yours in timing
