Well, it certainly looks like you have lots of space to do whatever you want. Very nice. Does your spouse plan on bordering the new 20X30' raised bed with wood? If not, it sounds more like an in ground garden to me. When I think of a raised bed, it is more the type in your other picture where you can reach into the raised bed without having to walk into it. But my neighbor made a raised bed that is 8X8' and she does not mind stepping up into the bed and taking care of it. So, I guess it all matters what you want.
Yeah, I have lots of old rotting wood stacked up by the garage. So this spring I made some new hügelkultur raised beds that are 16" high. I filled the bottom ~10" with the rotting logs and other wood I had, threw in a layer of old leaves, and topped it off with about a 6-8" layer of good top soil and chicken run compost mixed 1:1.
We have had almost no rain this year, so the only plants growing good at all are in my hügelkultur beds. In theory, the rotting wood is supposed to act like a sponge and release the water slowly to the plants. I think that is what is happening in my gardens. My "normal" raised beds are just too dry and the plants are suffering.
Although not practical for a 20x30' garden, my best performing design is my 2x4' elevated sub irrigated planters. They hold lots of water in the bottom 3" of the planter and my plants never go thirsty. Last year, with normal rainfall, I think I only had to refill my sub irrigated planters maybe once per month. This year, with high heat and no rain, I have to refill the planter almost twice a week. Still, I just put a garden hose into the fill tube and it takes only about 5 minutes to refill the planter reservoir. I made a water level indicator by cutting a strip off a swimming noodle and sticking it into the fill tube. When the indicator drops level with the top of the fill tube, I know it's time to refill.
I sprinkled seed instead of trying to make rows. I'll just thin the plants as needed.
