I wouldn't try TJ for the meds - most likely going to be sold baking powder in a capsule. If they can go a bit further east along the border, to Tecate, and have someone walk across the border for them, about two blocks straight down the main street, on the left (past the pottery), is a pharmacy that will take US prescriptions. I had to go there to get asthma meds for a cat once (no, really) and they sold the albuterol to me for $10 a vial, rather than the $195 the local pharmacies wanted. The cat improved, so I know it wasn't a dud canister.
Of course, that was a few years ago and I'm not sure the place is still there. Or if they'd even stock the meds your folks need. I'd try Canada, if it were me.