Having had experiences working with a diverse clientele in your family's store is very good. The experience of interacting with the poor and having a familiarity with the regulations around Food Stamps and the living situations of the poor is not a common one among med school applicants.
Translating for parents is a pretty common essay... it is a reasonable topic. Do keep in mind that your language skills should already be listed on the AMCAS.
Side note: Mail can be a plural noun. No "s" at the end.