Are you sure the bigleaf maple seeds were ripe? Possible, but it seems about a month early to me. Best sown soon after harvesting, if you store and let them dry you'll want to soak (2 days) before sowing. They don't need frost, but will need approx 2 - 3 months of moist chill, temps averaging 40 are fine.

Same with the dogwood/cornus. I don't know which you have but some will benefit from a few weeks of moist warm before a period of moist chill, so if you have them now, sow them now.

You'll be sowing now, and watching for germination in Spring after they've experienced a range of temperatures while moist.

You may have enough room for a tree which can reach 90 feet, and you may not object to digging out many seedlings which grow as fast as weeds, but you should think about this before planting Acer macrophyllum. Al

I am growing a few dogwood/cornus from seeds. I have not had much luck with purchased potted dogwoods. I agree with planting the seeds outdoors now. Let the weather do its' thing over the winter months. My cornus floridas only got about 3" tall the first year. Others grew faster. Protect them from wildlife chewing them up. I stake a "tube" of chicken wire around them. Then I don't run over them with the lawn mower either. Keep them protected for several years (or longer).