Like Dino and rbertalotto above, I suggest going cheap. A Fosi BT120A has Bluetooth and ample power output to drive speakers to dorm room levels. Give him a household chore to complete so he earned it himself. For speakers, Find a good used pair that fits his room size and musical tastes.
Looking for an all-in-one just-add-speakers streamer for my son to take to college
Cambridge Audio Evo 75 is probably the top of the range, but maybe a BlueSound Powernode is good enough? Maybe there is something cheaper that fits the bill?
My son is not (yet) an audiophile, so sufficient volume may be the most important, but interested in any thoughts folks have on this topic.