Hi megmaine, WS is so much fun and you will love it!! This is the Canadian forum and it is fairly quiet. I see that you are in the States so I will direct you to the other WS forum that is far more active. (not that we aren't happy to have you here) and you are sure welcome to hang around, but your questions will get a much quicker response over there.
To answer your question though, I put my containers under a small Japanese lilac tree that is outside my sunroom door. it provides dappled shade until mid afternoon when it becomes full shade from the shade of the house. Once the seeds sprout, you will remove the top of your containers so the heat shouldn't build up in the container anyway. I tend to keep my containers out of full sun because as I am at work I don't feel I can keep them monitored as far as moisture goes. As they grow, and if I am going to be home all day and can make sure they don't dry out, I may move some of the ones that have larger sprouts, out into the sun. once they have their second set of leaves, you can plant them out in the garden.
Hope that gives you an idea of where to put your containers.
click on the link below to go to the other WS forum.
gg

Here is a link that might be useful: WS