We got some mandarin oranges from the store and some of them had seeds. The kids stuck them in a pot of soil, and 3 have grown. Will they grow and bear fruit or are they wasting their time? How do they maintain them? Is there anything special they need to know?

Thanks

You can grow...
But, usually it will take a couple of years till they will bear fruit. How many years, well... I guess none will be able to tell you.
I have seen trees whch had come after 8 years to flower and fruit, but found more often tress with more than 20 years and no sign of flower and fruit...
So, yes you can grow, but no not expect fruits coming early....
Patience, often much patience will be need....

But usually most here start with a seedling, and got infected with this citrus-virus....

As Steve said, they will take a few years to produce fruit. Mandarins are usually in the 5 year range before producing fruit from seed. Being that you are growing them in the house in Canada you should expect a few more years before producing any fruit.

Thanks for your answers, I guess we will keep growing them until they get bored of them. Then I may take them over.

Thanks again.