I think that Adele would be ok, but the best one I could think of is the band Imagine Dragons. This band would be very easy to make quests for, I believe. Some very kid friendly artists include Bridget Mendler or Debbie Ryan. You could also start doing Nickelodeon stars such as Miranda Cosgrove. I am not so sure about these next characters, but they would be interesting to incorporate in the game for a few quests, like in Wizard101 with Selena Gomez. Some characters from the Hunger Games cast could be used. Just a few thoughts, and I hope this helps!