Weddings can be great fun for children, but of course there can be waiting around and boring bits too. With a little prior planning, you can make some simple ways to keep them happy throughout the day. At the start of the day when you're getting ready, have some colouring books or a TV in another room to keep kids busy. It's great for kids to watch and enjoy the ceremony, then afterwards have some games and activities for them to play - or even have them involved in helping pass out nibbles etc.
During the reception, one of the coolest ideas I've seen was a kids' table with lots of colouring books and even a paper table cloth they could draw on! Just remember, whatever the kids are doing, make sure they have lots of options and that they can do them quietly. Finally, if you do have a few children, consider bringing a minder along to care for them. Not a wedding guest, maybe a cousin or friend that can look after the kids all day for a few bucks.