Should I install tamper resistant receptacles
I doubt it's required for existing construction and repairs, depending on where you live; some states have not yet adopted the code but it looks like most (pdf) have; 

The incremental cost is small and if you have small children, it'll save having to buy those plastic inserts. And since I'm one who vividly recalls being a toddler a long time ago getting his first lesson in electricity after finding out that a metal coat hanger fits nicely in a wall socket, I think it's not a bad idea.