What most Americans would think of somone showing up on Easter (whom they had hired) to do tree work?

I would be highly embarrassed and would send them home. Easter is on Sunday and is even more important than Christmas to Christians. Memorial Day too is a day to honor those who have died for the United States and yes hired workers would not be appropriate. It has become a shopping day for some, and it has been on the TV news that it offends many people for stores to do that. It is OK to have family and friends over to barbecue. I would say 75 to 80% do that. We also watch TV programs of the President visiting the graves of soldiers and programs about wars we have been in. Those who use Facebook usually say something about Memorial Day and our thanks for freedom.