Congrats first of all!!!

I think if you really want a Saturday wedding, you can have it on a long weekend as long as you send out Save the Date notes a few months in advance.  That way, people will have plans- plans to go to your wedding!  When you request addresses from people, also make sure you mention the date and holiday so people have it in memory.

As far as a Sunday wedding, rarely would a wedding place book something for Sunday morning or lunch since a lot of people do go to church.  Try to have an early afternoon or evening wedding and it should be fine.  I am having my wedding ceremony at 4:30 pm on a Sunday with dinner reception to follow.  One thing to consider is that a Sunday wedding may mean that out of town guests have to take Monday off from work, whereas people can fly out Friday night and back Sunday if the wedding is Saturday.  The majority of our guests will be local, so this isn't too much of an issue for us.  Also, if cost is an issue for you, Sunday reservations are usually a lot cheaper than Saturdays.

Good luck with everything!