Welcome to THE SPACE SHOW

Five children save the life of a dog-like alien while at a self-run summer camp. He attempts to reward them by taking them to an alien colony on the Moon. Events take a turn for the worse when his report on that attack that injured him causes passage from the Moon to the Earth to be banned, and children are stranded in space. The children need to find a way back home before camp ends and their parents discover that they are missing. They also have to avoid the poachers that injured their alien friend, and now seem to be stalking them all.

Synopsis from Anime News Network