I would not do this if I were you. First, the lounges are extremely uninspiring. They are usually crowded and have limited options relative to other lounges that are used for int'l business class passengers. Second, the tram between T1,T2,T3 and T5 is not running due to construction. So you would basically have to leave T3, board a bus, go thru the TSA in T5 which usually takes me ~20 minutes. On the return you have to wait for the bus and then re-clear TSA in T3.

I know free is always a good thing. But I wouldn't attempt this for some picked over processed finger sandwiches and free drinks.

I'd either burn 300 Business Extraa points for a AC day pass or head to the Rick Bayless place. It's really good and worth the money.