we want to plant a small grouping (5-10) of apple trees. what kind is best to plant?
Washington County Minnesota apples
These publications list different varieties and their best use: http://www.extension.umn.edu/garden/yard-garden/fruit/apples-for-minnesota-and-their-culinary-uses/ , http://www.extension.umn.edu/garden/yard-garden/fruit/apples-in-home-garden/index.html. As discussed in these links, you will need to plant at least two varieties that bloom at the same time for proper cross-pollination.
regarding planting of 5-10 apple trees. we have an area on our land that has great sun but is adjacent to what is described as an "intermittent stream" (ditch that channels rainwater). would this situation negatively affect the land on which to plant the apple trees?
This shouldn't be a problem.