Ask any family who has traveled together and they will tell you stories of changing diapers in odd places, giving up a tour in favor of naps or cutting a hike short to find tums for kids. Traveling and sightseeing with children always includes interruptions such as these.
Instead of being surprised by these unexpected situations, be aware that they will come and plan to be flexible. If necessary, stop traveling early for the day, slow down for little legs to keep up and even exchange activities that you planned for more practical ones. Remember: The best part of traveling as a family is not visiting every historic spot or taking every available tour. The best part of a family trip is doing things together.