Answer:
A little pool with two layers of wall around it. One white and soft and the other dark and hard, amidst a light brown grassy lawn with an outline of a green grass. What am I?
I am one small little piece of paper yet sometimes hold lots of value. I am all you need to get in to big events but will cost you. I am an important part of travel. And if lost you're not coming.
Send poorly behaved children to me and let them sit here.
When I get closer my tail grows longer but when I go away my tail leads the way.
Soft and cuddly I'll pull on your heart. But take my last name and I'll tear you apart.
Give it food and it will live, give it water and it will die.