Translation:De går i kirke om søndagen.
Is is possible to say 'De tage i kirke'.
Also, when is it correct to use 'tage' or 'gar' (sorry no danish keyboard here).
I always thought 'gar' was when you physically walk somewhere. Not just to say you went there regardless of how you got there?
I understand where you're coming from with the connection between the English "to" and Danish "til". In this instance, however, the only acceptable form of "to go to church" as in attending service or other religious events in a church, is "at gå i kirke", lit. "to go in church".
I don't know if you're Danish or not, but I just asked a Dane which said that they do normally use 'går i kirke' but you can also use 'går til kirke', where the latter is older Danish. Just like how in English you can also say 'I go in church', just that it's used less often.
I am Danish, haha, but I have never heard of "at gå til kirke" ever, but then again, older Danish is not spoken in my social circles. Anyway, I'm sorry.