I don't care where people sit, actually. If I put someone in a specific spot, s/he is GOING to rebel and there really is no way to force family unity, you know? People will just switch the cards. This way, folks can be comfortable and 70 people (OMG!) isn't so many that folks won't wander and chat.

Actually, the idea of each table will be the same : fire, photos, living thing, favor - how it happens though, will be pretty relaxed.