I'd say that was very small - why not think about shrubs instead? Any tree will cast shade and take some light off your plants, lawn, you, your house, too.

There are a few to consider, having said that. A rowan tree is a good example, or a crab apple. Maybe even a small variety of Amelanchier? You could consider an upright growing tree, too - there are several evergreens, or an upright Prunus..

I was going to say crab apple too, they are very pretty.

Maybe one of the new columnar apples, such as 'Maypole'?