Personally I would go with HO scale for the fact that the larger pieces pose “less” of a hazard to kiddies then the N Scale.

As for minimum radius and stuff, may I suggest Robert Anderson’s E Book located somewhere here on this site, followed by purchasing ‘Model Railroader’s’ “Track Plannin for Realistic Operation” to aid in starting out.

Actually both books above I highly recommend having used both myself and have been very helpful in helping me answer the questions you had.