As with all of these tips, a professional wedding planner will be able to handle all of these issues. So please HIRE one! But in case you didn't...
Think about your reception as if you were a guest. How is the parking at your venue? Most churches have adequate parking, but what about your reception venue? Will your guests need to park several blocks away? What about grandparents and your older friends/family? Will they be able to walk the distance? Does it have enough outside light? A lot of single women attend weddings by themselves or in a group of girlfriends - will they feel safe walking out to their car after the reception is over (or before it is over when fewer people are outside)? What if rain is forecasted? Having extra umbrellas might be nice.
I don't think that, if the parking situation is inadequate, it should affect your decision on the venue, but it is something that you should ask the facility. Some venues provide golf carts to carry guests back and forth to their cars. Maybe valet parking is a must. Or maybe have a "bulky" (sober) groomsmen help people get to their car safely. Just have a plan.
"It’s a beginning and an ending, it’s glorious and sad, and it’s intimate and public. In your lifetime there will be few milestones that will change the course of your future more than your wedding day. Main Street Productions understands and believes in the emotions of life. We bring these emotions to our art and look forward to presenting you a glimpse into your own past." - John Deaver, Main Street Productions