Accessory Activation

You can do both. Wire in the momentary push buttons, and then a SPST switch to connect to the insulated rail when/if desired. Some accessories won't be as bothersome as others.

Like everything in life, it depends.  Mostly upon who your taget audience is.  I have a small layout with many pushbuttons on it.  Children of all ages love it.  But what is quickly annoying to adults kids love.  I am thinking of ringing bells, whistles, and the gateman going in and out of his house.  Kids can't get enough of the gateman.  I haven't had any problem with wear on anything.  All of the accessories used are really pretty simple: a solenoid or a small motor of some sort.  I am amazed they still function.  I originally had some concern that the solenoids would overheat and had considered putting in a timer so that the pushbuttons could not immediately re-activate the accessories but there have not been any issues.  I have seen this issue with accessories which were activated by a control rail and a car just sat on the track keeping the solenoid activated for an extended period of time.  Ask me how I know.  As Rob has suggested you could put a "secret" SPDT switch which would toggle the accessory activation to ether the pushbutton orthe control rail.

Don