I'm a big fan of Grandaddy Purple and for years have been running my own inbred beans of my line all the way up to an F9 generation now. Quite a bit less experience with Blue Dream, but I have run out females four or five times. They're both very good strains, but I'm definitely partial to the GDP.
The only thing I would caution you about while you get growing is the differences in structures to these two plants. The GDP tends to put out shorter, squat girls with some girth to them depending on the phenotypes. The Blue Dream is more "Sativa" leaning, so the plants you have in that line might stretch out quite a bit more into flower than the GDP. You can control that, of course, but it's definitely something to keep an eye on.
The GDP is easy to finish solid in my opinion, but the Blue Dream takes a little more work. With the Blue Dream your grow, dry, and cure have to be pretty much spot on to get the most out of it -- you know, flavor profile, effects, etc. But people really seem to like it even after mediocre grows and finishes, so I don't know.
Anyway, I'd say just beware of your stretches during flower. You won't want your Blue Dream to crowd or shade out your GDP. They'll likely also have different nutritional and elemental needs, so it's prob a good idea to be aware of that, too.
Seedlings look happy. Best of luck with 'em!