Do they donate the clothes in the end or just throw them into the trash?
Also, you don't need to literally kill all virus particles. Reducing their number already reduces the probability of getting sick. A certain amount is needed to attack you successfully; a lonely virus particle is mostly harmless. Also, the virus cannot enter your body by being in the clothes your wear, only if you touch the clothes and then your mouth/nose/eyes.
tl;dr - yes, if you wash the clothes and leave them dry for a few days, it is safe