The lowest cost would be to have everyone drive themselves but I assume you have already thought of that idea. Here are a few good things to keep in mind if you are going to look in a limo. Because it is a Sunday, look at the possibility of a "pick-up" and "drop off" this can sometimes be cheaper then renting a limo for the whole stretch of time. It is limo "off season", try negotiating. Call around, most limo companies will price match because they want the business. I hope this helps.