My wife is from Venezuela, but technically she's half Colombian, as her mom is Colombian. The main Venezuelan dish is the arepa, made with a specific corn flour brand from Venezuela called Harina P.A.N. which luckily can be found at Fred Meyer. And yes lots of plantains too. But other than that I don't have too much advice to give cause yes unfortunately there aren't any dedicated Latin American stores except for Mexican stores. There is a nice food cart pod in SE Portland called Portland Mercado. I've never eaten from the Colombian food cart there (Qué Bacano) but I know the owners of the Venezuelan food cart (La Arepa) and I highly recommend it. Could maybe be cool for you to take your son and his girlfriend there when all this craziness ends.