Yep, you can keep them in the same tent so long as there is ample room. Grow medium depends on your grow method.
Do you want to grow Organically? Hydroponically?
How big do you want them to get?
What kind of lights are you using?
Do you have an area already set up for your new babies?
What kind of equipment do you already have?
Have you already germinated them?
Basically, a quick summary of your grow method, equipment, etc will help us with helping you a whole lot more.
GL