I have the same issue, a huge willow tree at the west end starts shading at about 3 pm. Last year my tomatoes did fine. Also that late partial sun keeps them from burning to a crisp during the late hot summer. They should be fine.

I'd be happy to have that stretch of morning to afternoon sun. I get the opposite...mostly shaded until 2-3ish then scorching direct sun until sunset...they still do fine if I can keep the fungi at bay! :) I bet they'll do well...perhaps lighter yield, but "ideal" growing conditions are just that...an ideal!