Redbud grows wide and flat. A tree only 10ft tall will have branches that spread that much or more. Same with Cornus florida, the most common tree Dogwood. You might check on Chionanthus virginicus, Fringe Tree. It needs good drainage, but with minimal pruning you can keep the width to within your needs. It grows denser than a Redbud or a Dogwood and is native.

A large shrub would be Viburnum recognitum.

Here is a link that might be useful: info here

Fringetree

Hmmmm.... Just to be odd I will throw out the evergreen hollies. Even if you go main species if ya get more than 40 feet during my lifetime I would be impressed. I have two, probably mislabeled as the species, which are flowing heavily enough right now they are quite attractive. The berries on the one by the street are still there, the other's have been gone some time.

Crepe myrtle would probably be more perennial than even shrub like in zone 5.....

Just thinking

Crab apples looked good even in Denver not sure given your specifics.

The Oxydendrum should do fine, if you go with a local seed source - They're supposed to be hardy to Zone 5, and I've seen one massive one in somebody's front yard just south of Lafayette, IN - This is a fairly cold, windswept area, as well.

Is there a reason you are only considering deciduous trees?
Lots of all season beauty with the many broadleaved evergreens (that flower) and colorful conifers out there!

Fringe tree came up twice -- do folks think it's better than the choices I name, or just another thing to consider? To be clear, I'm ok with a tree reaching 30-40 ft in both height and spread, which would take quite some time for both a dogwood and a redbud, no?

cearbhaill, I'm not limiting choices to deciduous, it's just that this is a spot not often seen during winter from inside or outside the house, so winter interest is not a primary factor. I'd definitely consider evergreens with good spring/ summer/ fall interest. The holly may be a good choice, too.

Franklin Tree (Franklinia alatamaha) is another option not mentioned....extinct in the wild so thats an interesting fact. Last known stand occured in Georgia but it does very well up north...was pushed south in the last ice age by glaciers and was unable to reestablish itself up north. It flowers in fall at the same time its leaves start to change color...which is unusual.

I love the native redbud, especially when in bloom. The leaves are nice too in summer and then there is a good yellow fall color.

Here is a link that might be useful: Redbud flanked by ostrich ferns

But they are not long-lived at all. We are about to underplant the one by our back door. This will be the third in less than thirty years.