I've always used "Outings" as a sort of party on Comunity lots. You still get a score of sorts, but no memory. I know it would be more realistic, since real life family reunions are probably usually held somewhere other than a private residence, and the Family Reunion memory only happens with a party.
I really don't understand why EAxis designed it this way. In reality, people have parties at parks and restaurants all the time. Think of all the little kids birthday parties that happen at McDonalds. And office parties that take place at bar and grill type venues. But in the game, sorry, you can't have a party anywhere other than your place of residence.