Use the adjective beamish when you describe someone who is smiling and cheerful. A beamish child tends to laugh and play happily with his friends all afternoon.
Though it's unusual, beamish is a descriptive way to talk about a smiley, optimistic person. Your kindergarten teacher may have been beamish, cheering students up with her positive attitude and sweet smile. Most kids are beamish when they visit amusement parks and playgrounds. Beamish dates from the 1500's, from the verb beam, "to smile radiantly." Lewis Carroll may have thought he invented the word in his poem "Jabberwocky," which is full of made-up words, but beamish is real, if uncommon.