I have been growing things in my backyard, starting with veggies in containers and now branching into edible foundation plantings (elderberries, goumi, spicebush, mulched with comfrey) and a greenhouse (mostly figs), for several years. I have just put in a permaculture container garden in the back yard, near my greenhouse. Now we have had the lateral (a big sewage drainage pipe) replaced in front, leaving the south half of our lawn denuded except for foundation plantings (Knockout roses, ornamental elderberries [my favorites!]) and hostas on either side of the walkway. I am staring at a 32 by 27 foot stretch of former lawn, denuded of topsoil, somewhat irregular in surface. We live in Zone 7a. We were getting a lot of cardboard, but I fear it was mostly put in the recycling before the lateral was dug (I had no idea they would rip up the entire southern half of the lawn). Hubby wants to plant grass seed; I told him it needed better topsoil, but he just wants to lay it on the brown bottom soil (Is that the right term?) exposed by the digging. I asked him if I could put in tree guilds or some other form of permaculture; he said sure; he just wanted the soil anchored, hence the grass seed. Is now a good time to get a few trees (I am leaning toward pawpaws; I harvested my first ones [and am still harvesting] this season and find them hardier than figs) and start some guilds, maybe an herb spiral? I can see I will need to plant more goumis and maybe divide my comfrey to beef up the soil, along with some bags of soil conditioner.
A nude space is a great place to start. maybe talk to your partner about mixing clover with the grass seed. or bringing in free woodchips for the perrenial forest. get some paper out, map the spot and get planning together!
I think converting it to a permaculture garden is great, and fall is a good time to plant trees.
At the same time, I think it would still be good to cover the remaining soil with something. Annual grass seed would work, with mulch placed around any new trees shrubs; however, there are other options for a winter cover crop that may be more beneficial, such as a legume of some type, or a root vegetable that can help add organic matter down below the soil surface.
Either way, it sounds like you have a good blank space to work with, and you are already on the right track with improving the soil while also making use of the space to obtain a yield of food for the family.