If your invitation says "& Guest" you are welcome to bring a plus one.
If your invitation says "The _____ Family" or "& Kids"; kids are welcome! A wedding isn't a wedding without kids according to Heather and Cassidy.
Well, it is a wedding... make the Brides feel special by pulling out your nice clothes. At the same time, not too fancy. The ceremony is outside so wear heels at your own risk :). The Brides will be wearing converse so... fancy on top and casual on bottom?! lol