At home party after destination wedding

I think either idea is a good plan, but I think Friday may be better. Memorial Day weekend can be very busy, so having it on Sunday may mean people coming late and/or leaving early. Friday evening would generally mean people coming after work and with no other obligations to rush off to. But if you want to have an open house feel and don't mind a lot of coming and going, the Sunday plan would suit better.

Unless it's much later (like 8 PM or later), I'd serve a full meal or a ton of appetizers. If I went to a party at 6 PM, I'd expect dinner. If you do it on Memorial Day weekend, I'd anticipate a lot of people not being able to go just since it's a popular weekend for vacations.