Try not to think in terms of "kids" or "teens" bikes.

Not to be redundant or critical, many older individuals seeking to re-enter the cycling world habitually select a bike based on $ and/or cosmetics. After 6 months riding, they come to realize that the initial purchase wasn't quite right, and the purchasing criteria has now change. Fit (comfort) and reliability become paramount. And if you are forced to haul the bike up a flight of stairs, weight also enters the picture.

So again, ride several examples which fall into your 'size' and price range. Color can be changed... and fenders, racks and accessories can be added later. Happy hunting.