I don't want to spoon feed you but these may help :)
a) a character: your sister, your bestfriend, your father
b) a journey: to me fantasy will be fun and these will be the points:
-play in the park
-saw a map and follow it
-reach your destination which is a big mansion
-there were friendly dragons and heros
-had a fun day
-go back home
-the adventure will stay as a secret