Meh, far as I'm concerned they can still talk about all these events and facts but they should always do so in a positive and celebratory manner.
Not, this site remembers whatever genocide, but instead, this site remembers the soldiers/citizens who faught against a ruthless group who were at the time commiting genocidal acts against indigenous people... You don't even need to name the group of assholes. But it's fine to specifically name the heros and their heroic acts.
Perhaps post education signs that talk about positive changes to an area.
Like in 1998 John Soandso lead a campaign to restore the area you see before you to the healthy natural state it's in today. Because of that campaign bla bla birds and native plants have returned to the area over the years since. Previous to John's campaign the area had been heavily over polluted by nearby industrial factories.
Keep any of the bad stuff referenced as a relevant afterthought. Use the good stuff as examples of what to do, of people to look up to.
I saw some similar signs in NC last time I went through, like the ones celebrating the life of a master builder in area who had helped build many of the still standing historic building. Oh yeah, he was also black and a slave, but that wasn't the point, so it was just kinda noted within the context of the details of his life... Instead the sign celebrated his craft and contributions to the community.