Jason, Bluebirds don't eat birdseed, and I've never put anything in the house to attract them. There is quite a ruckus when they arrive, with everyone fighting over the two houses in the daylily garden. There is always a broker out there trying to schedule showings, but all the birds show up at once, and fight over the real estate.
Between the Bluebirds and Tree Swallows, they have the area covered! I also have about 10 other houses up around the fence line, and they are all full. I always keep seed out for the other birds too. One thing I've noticed is that the Bluebirds love taking baths, but I've never seen another bird taking a bath here. So, maybe a bird bath in the area would help? Just make sure that the houses are hung where they are in an open area. I don't believe that they will nest in a house attached to a tree, unless the rest of the circumstances are to their liking. They want an open area below them, so that they can look for bugs.
Pam, I do have a tree cam, but it won't work in the daylily garden. They are motion activated, and with the wind never stopping here, the foliage on the daylilies would set it off all day long.