Gallus, why is everything brassica? I'm upset? How am I supposed to get a crop rotation going, in consideration of soil, climate and what this family actually eats, when everything, I can think of, is brassica? What were our ancestors thinking?
"Why are all crops Brassica?" is like asking "Why are all dogs wolves?": Because we found ONE very genetically manipulable species and pushed it into as many fun and exciting shapes as possible.
HOWEVER, Like how we also have Cats, Chickens, Horses, goats and Pigeons, we also have:
Nightshdes: Tomatoes, Potatoes, and every kind of pepper except black pepper. Like Brassicas, they need a lot of calcium, so you shouldn't put them in the same bed, and supplemmenting both beds with finely crushed eggshells will help.
Cucurbits: Summer and Winter Squashes, melons, cucumbers, Chayote, Pumpkins. Not as demanding about the calcium, do need the kind of sun that will literally Sunburn brassicas and nightshades to death.
Alliums: Garlic, Leek, Onion, Scallion. What are you doing if you don't have these???
Special shouthout here to CEREALS like Corn, Sogrhum, Wheat, oats and Barely, which *can* be grown in a backyard garden if you are insane.
BEANS: Look. There is some bean somewhere your family will like. Black beans, pinto beans, peas, lentils, chickpeas, and PEANUTS.
There's also Carrots and parsnips, but they have weird sandy soil requirements so they require a similar level of dedication and research as cereals do.
And that's just vegetables! You also have "fruits" which for purposes of this post are "assorted sweet-tasting plant parts", including but not limited to:
Strawberries, blueberries, Raspberries, apples, pears, peaches, plums, currants, cranberries, and cherries all of which I've grown in my yard before.
You've also go HERBS, which are generally not related, but you can interweave them between larger crop plants to keep your biodiversity up and help prevent disease outbreaks by acting as physical barries between plants: Rosemary, Thyme, Dill, Sage, Parsley, BASIL, Savory, lemongrass, and Mint if you're nasty.
I have to believe there's a few things in each of these categories your family will eat. Look up the nutritional needs of each and you can probably swing a crop rotation schedule from there.