Does it have a different meaning than "we take a break at this time every day"?
In this context should "break" and "rest" not be interchangeable?
Just curious ... would it be OK to translate "bíonn sos againn" as "we usually have a break"?
Not really - "usually" would imply that sometimes we don't take a break, and you would use de ghnáth or go hiondúil to indicate that.
Would the "habitual" translation of "We do be having a break at this time every day" (although it's not standard English) be a good translation?
Taken directly from Irish, its a construction often heard in Ireland, although one might have heard, in this example, "We do have a break at this time every day".