Darling Wife has over 200 seedlings that need to get in the ground, pronto - else they're gonna completely take over the office

Pretty much every square foot of our ~ 2 acres is grass, including the areas she has picked out as best for the garden beds. Figure we'll be building slightly raised beds in 4' x 4' squares. Hence my question: what are my options for dealing with the grass?

Roots are ridiculously thick and run 6" to maybe 10" deep. Really want to do this right (Darling Wife has put a lot of effort into building purdy green things out of microscopic little seeds - and we're hoping to cut a measurable chunk out of our food bill as a result) but time (and my back) suggest looking at short cuts.

Can I simply buy/rent a tiller and turn the grass under, or do I need to scalp the garden area and replace the sod with new soil? Other options? FWIW, seeds and everything that has gone into them are organic - planning to carry that through the whole process, so agent orange to remove the existing foliage is out.....

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1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man - given away
1980 Redhead: Darling Wife