I think I would "test the waters" if you are planning on leaving items with gasoline in the garage and have your kids sleeping in there too. Before putting your kids in that room with the "toys", let them sleep on the master bed and YOU sleep in the garage one night and see if you get fumes. If you do, you'll know what you have to do.
I for one, would never sleep in the same space where gasoline is stored, in any type of container! I don't even keep gasoline store in the garage attached to my house. I also have a detached garage where gasoline is stored with all my mowers and stuff.
When we lived in town and the garage was attached to the hosue, I stored all gasoline items in a utility shed behind the house. No gasoline was ever under the same roof I slept under