According to what I read on the wiki, contemporary dothraki could go for k'atfirezari (elided version of ki + noun fire with circumfix ath__ar in genitive declinasion) but it targets manner adverbs, and I can't tell for sure if around is a manner adverb.
Well, in this case it'd be a preposition, since it has an object,
mori.
Ath- -(z)ar is for making nouns out of other classes, though, and
fire is already a noun. Looking over the vocabulary list, I see
gache, "place, environs". Maybe something like
she gache mori, meaning, "in/on their environs" or less literally "in/on the area where they are", might convey the idea of a thing happening in the general area surrounding someone.
K'athfirevenari might work as an adverbial form, derived from
fireven, "ringlike", so
k'athfirevenari would mean something like "by ringlikeness". Though, I'm not sure if that would necessary convey the same idea as "around", or if it would mean something more like doing something in circles.
Edit: Graddakh, I was very confused about
fir vs.
fire.
K'athfirari would be fine for "by roundness", I think, though I don't know if that really would work for "around" either.