Memorial Day is for those who made the ultimate sacrifice and died fighting in the line of duty, as you and your husband correctly state, but there is no harm done in tying the day to those who were and are willing to take the risk.
At Mass last night, Father Mike, an Air Force Reservist just back from Iraq, ended the service by speaking of Memorial Day's traditional meaning and asked veterans to stand. He reminded us that these veterans had been willing to lay down their lives as others had who paid the price. As representatives of those we honor on this holiday he then gave a special blessing. But during his remarks we in the congregation did interrupt with applause of approval.
I think saying Happy Memorial Day is clumsy but not thoughtless. I wouldn't do it, but if I heard it, I would take it as expressing happiness over our country and gratitude for those who serve her.
Thanks---very good way to put it in perspective!!!