I would like to have a patio, but I have my septic system and leach fields right where I'd like it to be. I have no preference in materials. I would like something low cost and easy to sweep pine needles, sand and dirt from. I also have three young kids plus their friends to keep safe.

Any suggestions?

You should not put anything over the septic tank, since it will have to be pumped

I agree, there is the tile field to consider and nothing should be put on top of this area.

Best advice, find a new location for the patio. Do not place anything over the septic tank.