I would like to suggest a French red Rhone for dry....many very good under $15. The labels will generally "look" expensive. For white, if sweet is desired, agree with Riesling, dry Rieslings, but not always, have a bit of sweetness if you don't want sugar wine... If they want sweeter, make a spritzer by adding Sprite. Gross IMO, but a fair amount of people like it. Regardless, wishing them a long and happy life!