I am kind of the wrong person to answer this question... as my FI's family has "potlucks" whenever they have a party and I was brought up as when you have a party you provide.... So I think it would be great to invite everybody out to dinner after your DW but I think that people may be expecting to have their dinner paid for since they are going to be invited... I'm sorry not trying to be mean if I sound it just saying my opinion..