Can someone help me?
Can't say gender specific terms (prince and princess), can't say boy or girl, can't say children (someone may be very small/short and mistaken for a child), wouldn't be good to say, hello person under the age of 18 (what if they just look super young)....
What should they be called?
I'm not picking sides, but there is no silver bullet option. I may be in the minority, but as someone that is in the minority, you just learn to let things roll off your mind/back and enjoy life. Life is too short to get caught up in words, ideas and boxes as such.