How do we fold this in when we are in the middle of another capital campaign or centennial celebration? Especially when we already have a brand?

This will hopefully be a part of your annual efforts and can be woven into your communications at the appropriate time of your campaign. For example, leveraging the #LibraryGivingDay hashtag and momentum is fine without using all of the logos. Using the logos is always a great idea for a unified look, however, during special years you could choose to minimize the use of the logos and tie in the concept in your messaging.