There is nothing in the Quran and hadith that prohibits what you have asked about. However, it is essential to check if the region is clean or not as khabaith is strictly haram [7:157].
Among the scholars, there is a difference of opinionsource. One group completely forbids it to avoid sin, other group expresses permissibility, some with reluctance.
Hence you do anything as long as it is not anal penetration.
To resonate with your words, it is not haraam to eat the booty, but not the shit.
not haraam means either halal or makruh