Guest List and ex-wife/newwife dilemma

[Lovemypilot]

Hey!
I got some great answers on the last thread I posted, so I thought I would try again! I have two big questions and concerns about the guests. First, we are trying to keep the guests to 100 people, but right now our guest list is at about 160. Most of the guests will be coming in from out of town so I know not everyone will be attending. However, a lot of the guests on the list seem to be coming from all the +1 we are giving our friends. Do I really need to give everyone a +1? I of course would allow anyone with a bf/gf that they have been serious with, but I just dont want random people at my wedding when I have people on my list who mean more to me. Can I do that?

Also, second question is my DF's dad is divorced from his mom and got remarried about 10 years ago. but his mom and step mom DO NOT get along. How can I seat them at the ceremony so that they are not close, but still up front and also at the reception? I want to do a head table with our parents, but dont want them sitting next to each other. Any suggestions??