Having them in more shade now (mid-late summer) is no big deal, Joanna. When they're actively growing in the spring you probably want them in more full sun. I'd just make sure those things aren't self seeding in your peony's grow space.
As for what's expensive it really depends on your perspective, garden plan and budget. You can get a Sarah Bernhardt root from a big box store for a couple of bucks and it'll probably grow and give flowers in 3-4 years. You can buy a bigger, fresher root of the same from one of the big growers from online for somewhere around $18-25 and it'll probably bloom 1st spring after planting in the fall. The root from the big box store could easily (speaking from experience) not be the correct type and, while all peonies are pretty, if you really wanted that Sarah you'll have to start over and buy another root. Most of the big on-line sellers will send a true to variety root or will replace it for free if they make a mistake and you'll probably know that first spring. That larger, fresher root will probably be big enough to divide by the time the smaller root starts producing flowers and you could easily trade divisions for different varieties to grow your collection. And then you're addicted and start spending the $100 plus to get your favorite hybridizer's most recently released roots.....
