My friend is Irish and he is leaving my company. I do not speak any Irish but we have some internal jokes about "own lawn mowing" and the word "aon". A group of friends wanted to give him a farewell gift that would play on those words. We came up with the sentence "There is no higher purpose than to mow my own lawn" which was translated online to "Níl aon aidhm níos airde ná mo lawn féin a ghearradh"

I wanted to confirm that this is right.

Thank you all!

That translation is not correct. It uses the English word "lawn" for one thing. In Irish this should probably be translated with faiche. For another, I don't think the verb gearr can be used with faiche. In English you can say "cut the lawn" or "cut the grass", but the Irish gearr an fhaiche sounds strange to me, like it suggests you are cutting a lawn in half. Perhaps another forum member can correct me here if this is idiomatically fine.

I think it's typical to use an idiom like sin an chloch is mó ar a phaidrín "that's the biggest stone (i.e. bead) on his rosary" when discussing something which is most important to a person. Unfortunately, I can't think of a way to make that work with your word play.

In any case, I'd suggest you go with one of the following translations:

Níl aon chuspóir níos mórga ná m'fhaiche féin a lomadh - "There is no greater purpose than mowing my own lawn"

Níl aon chuspóir níos mórga ná m'fhéar féin a ghearradh - "There is no greater purpose than cutting my own grass"

Thank you very much