Post a picture of your yard for reference.

How about a retractable awning? It would give you instant gratification.

How about a serviceberry or ornamental crab apple? Many varieties reach about 15 -20’ or larger so they can block sun for a ranch home.

What do you consider 'small'? Your list of choices may stay somewhat narrow but not at all small in stature. And narrow doesn't provide a high degree of shade relief, regardless of height. Planting in multiples is also likely to overwhelm what is essentially a tiny plantable backyard.

Small trees for small spaces generally are best kept to under 20-25 feet - crabapples, redbuds, most dogwoods, Asian maples, hawthorn, some magnolias. The question is will these provide sufficient shade to be of value and will they spread too wide to fit in that narrow planting area?

I wouldn't be overly concerned about the possibility of Verticillium wilt being present in the soil. It is in most soils but stays dormant until prompted into activity by a stressed or damaged susceptible woody plant. I've experienced VW where it has killed a susceptible species but completely ignored several others very closely adjacent. Just don't plant a susceptible species in the same location as one that was infected and died and you should be fine.

tbh, the suggestion of a shade sail or awning or even a pergola if the budget allows makes the most practical sense.

One I like is 'Forest Pansy' redbud...

Also add Amelanchier to the list, maybe A. 'Autumn Brilliance' for fall color. Shade cloths are better than nothing but nowhere near the coolness of leafy shade from a tree.