You could check out Cornus mas "Golden Glory"? This might fit your requirements.

Dwarf conifers are a possibility - there are scads of varieties and many will never exceed 15' in a lifetime. Since they are evergreen, they look as good in winter as in summer, but they don't flower and they don't grow fast.

Evergreen flowering shrubs are limited for your hardiness zone but you could look at rhododendrons or pieris. Some varieties are more sun tolerant than others but again, none growth particularly fast.

There are any number of deciduous flowering shrubs that could work for you - lilac, forsythia, smokebush, rose of Sharon, chionanthus. These tend to grow more rapidly than either conifers or broadleaved evergreen shrubs but they are pretty much uniformly naked in winter :-) It is hard to find any flowering trees that wil remain below 15'....and even these generally tend to have naked trunks or seldom branch to the ground.

Personally, I would opt to create a larger planting bed somewhere along the street side that is appropriate to your screening requirements. And I'd use a mix of plants - something tall and full to provide screening, something that provides seasonal bloom color and something to give evergreen/winter attraction.

I know not everyone thinks this way but a tree (or two) or even a large shrub plunked down in the middle of the lawn looks to me extremely awkward and disconnected. Even less appropriate with a small garden such as yours - it comes across as a bit of an after thought instead of a planned landscape. I would much prefer to see a well thought out planting bed with maybe a larger tree to anchor it and smaller shrubs as an accompaniment.

Thank you for the advice.
I do agree, i think it would look odd to just have a random shrub in the middle of the yard. we do plan on doing a curved bed on the left side of the yard from the corner of the fence coming to the front and then over a few feet to the right. like a triangle shape. we were going to do a mix of some evergreens and small shrubs and some sort of groundcover. we were also going to do a smaller curved bed on the front right corner with a small shrub or 2 and some perennials. i was thinking of doing azaleas in front of the windows and then maybe a lilac in front of the railing. there is a bed lining the front walkway that has perennials. hope this gives more of an idea- just looking for something with a little height in the center of yard. unless we should just skip that part.