Broadcast sowing into lawn - cover crop polyculture

Hello everyone. I have about an acre of weedy pasture (lots of quackgrass, some brambles, some wildflowers) that I would like to turn over to gardens, nursery and food forest. My plan this year was to broadcast a bunch of random cover crops + extras, harvest what I can, slash what's left this fall and sheet mulch over it. I'm hoping to improve the soil this year and obtain a yield, I don't have the time this spring to sheet mulch, but I will this fall.  

My question is, is this just a waste of seed? Stuff online says to rake first, but I'm assuming that is in garden beds - too much grass in the rhizosphere right now. I might as well till (I don't want to till). If I mow first, is there a chance that these things will come up through the grass? FWIW I'm planting buckwheat, oats, field peas, yellow sweet clover, daikon radish, cowpea, kale, and winter squash. I can time it before a rain this weekend. Any thoughts on how to proceed or is this a fool's errand?

i would try to broadcast the seed then mow. The grass will act like a mulch and will also shield your seeds from the eyes of birds. Then pray for the right amount of rain and sunshine. Broadcast pretty heavy.