You can actually see the property (and other hotels/Gateway Gardens area) standing outside of Terminal 2.
The odd part is just walking down the exit from T2 (where the cars drive and sidewalk is very narrow) but after that there are just a few streets to cross with traffic lights. its safe to walk imho, but its at least 15 minutes and I would probably just go to T1 and drive one station with the S-bahn; especially with lugagge.