I am sorry to hear about your trees. In answer to your questions, it is your decision on how to proceed with your non-infected ash tree. Healthy, mature trees improve the attractiveness of a landscape and as you note, can provide much needed shade. You obviously like your tree and if you want it to live you will need to treat it although treatment cannot guarantee that the tree will never become infected. EAB will cause the demise of most unprotected ash trees and is expected to be around for years to come, based on the Minnesota tree base. The decision to remove infected trees depends on several factors, including the extent of the infestation, the tree's overall health, and the potential risk to other trees (your healthy ash is at higher risk given its proximity to the infected trees) and structures in the vicinity. Removal is often recommended for severely infested trees. Removal costs can range from several hundred to several thousand dollars, depending on their size and location. Removing an infected tree does not cause it to spread EAB if you (or tree removal company) follow recommended guidelines. Here is a link to the U of M Extension Yard and Garden website about Emerald Ash Borer (EAB): https://extension.umn.edu/tree-and-shrub-insects/emerald-ash-borers#should-i-treat-my-ash-trees%3F-1472160. It discusses treatment and removal of infected trees. Good Luck with your decisions.