Maybe I am in the minority, but I would ALWAYS assume that my kids were invited to a wedding unless it specifically said otherwise. My wedding? Not only did I invite many of my professors - who worked with my mother - but would have been upset greatly if they had NOT brought their kids. These were NOT people from out of town, and they never questioned if their kids could come, though the invites went to the parents. I know ONE mom, a professor that I didn't have but who's prof husband I had in quite a few classes, also a family I babysat for extensively, said she was bummed because the reception was so informal (I wore shorts that matched the top of the wedding outfit - and it was pink and mint green with tulips on the fabric - NOT as awful as it sounds, actually very pretty or so I was told by my daughter a year ago, lol) that seh didn't have even one chance that summer to make her girls dress up. Her girls, on the other hand, thought it was super awesome to not have to dress up and wear tights or hose or whatever in Aug in OK.
I can only think of TWO weddings where my kids were not invited. Both times it was coworkers of husband and a ceremony later in the evening and relatives of either the bride or groom had a child or three who could not come close to behaving and both times the fear was that these kids would not be supervised by parents and would set the place on fire or hurt someone. I am talking difficult children of 8-12yo. We were specifically told that our kids could attend but figured they wouldn't have much fun being the only kids there. Also Wiz didn't do so well with big changes in his schedule at the time.
There have been VERY few weddings, even adult only ones, where we were not told that it was okay to bring our kids. Even Wiz somehow managed to be charming enough that others wanted him there when they didn't want any kids. I found it bizarre, but was glad that all the hassle and PITA of insisting that he KNOW decent manners was good for something. (If you KNOW decent manners then you have a choice - if no one teaches them to you then you don't have much choice, esp with the social issues that difficult children have!). I do remember refusing to take Wiz to a wedding. He was 7 mos old, I was matron of honor, the ceremony was a huge dog and pony show with three hours of photos before the wedding and two hours after, then a reception forty minutes away from the church. My aunt was babysitting Wiz, but he hadn't really been away from me for long. My aunt had a child six mos older than Wiz and was preg with her second and about halfway through the ceremony Wiz refused to take a bottle. I actually didn't go to the reception. Bride actually EXPECTED me to allow her 80+yo Gma to babysit Wiz during the ceremony and reception. this was a women who used to sit and play wedding dress up with us ALL the time when we were kids. I can remember being eight or so and hearing her tell us that our weddings would be something she would cherish seeing. NO WAY would I even tentatively ask, much less expect, her to babysit during the ceremony.
I guess our family just doesn't exclude kids from stuff, so it wouldn't occur to me. I do have a second cousin who's bride decided just before the wedding to not let kids come, so instead of the big audience there to fill the church and then go to the reception, she had about half the people because it was too short for many to get sitters. She was REALLY bridezilla about this, and apparently had a fit about it.
I think if you are travelling a long way to get the ceremony, and the couple does not want kids, they should recognize that many families cannot find/afford an overnight sitter and they should set up something really nice for the kids.
Sorry about the drama. I hope that no one decides you are being "mean" or whatever by not letting difficult child babysit - sadly it may come as another source of conflama.
. Often there are hor'devours as well. Cost is around $75-100 per person (some places have a child's price but it is still $50-75/child). 
