I can relate on the choosing the date! We were originally going to do it April 2015, then got pushed back to january/february 2015, then December 2014 and now it is officially moved to November 11th, 2014. Talk about stressful. Trying to pick a date went on for a week, trying to make sure the nearest and dearest could make it and we still have some people complaining but I've learnt there are always going to be a bunch in the pack no matter what date you choose. I just made sure immediate family could make it and those I wanted to be my bridesmaids and even then, one may not be able to make it.
You still have some time to see who will make it, you have over a year and half. Like csho said above, I would hold off asking maybe until a year before. You are giving people MORE than enough notice, so I can't see why people would complain!