Do all outlets in detached workshop need to be tamper resistant?
Yes it is required by the 2014 NEC, the 2014 Code says:
406.12 Tamper-Resistant Receptacles. Tamper-resistant receptacles shall be installed as specified in 406.12(A) through (C).
(A) Dwelling Units. In all areas specified in 210.52, all nonlocking-type 125-volt, 15- and 20-ampere receptacles shall be listed tamper-resistant receptacles.