I think it might depend on how stubborn a kid is: I would
suggest explaining your reasons for your suggestions. Since they
are younger, they are most likely open to your suggestions if you
can communicate clearly the pro's and con's of one actions.
If they are not willing to accept your reasoning, you have to be a
little more harsh and put them in a situation that condones your
reasoning. The reason that people (not only kids) act rich and
spoiled is because they are in their comfort zone. Once your remove
them from that comfort zone and remove all the power they think
they have - you're on the upperhand. It is at this point when they
are most susceptible to suggestion. At this point, you must also be
a guide for them. You have to be clear on what you're trying to
express to them. Don't confuse them with the theory, instead, use
"cause and effect" examples.
I don't have any kids of my own, however, I work with kids and
stubborn people on a daily basis. 
- Sam
