2 hours sounds about right. POR is lovely and if you have time, I think worth a stop. OKW is nice but I personally like POR's grounds better. If you go to POR in the evening, stop in at the Riverside location to catch Yeeha Bob's show in the lounge. Well worth it.
The boat ride only takes about 10-ish min itself but you may have to wait for a boat at any place. If you are staying at SSR, it's faster usually to just walk over to the boat dock behind Rainforest cafe and take the boat directly to POR. I've done this several times. Especially with the new walkways at DS, it's easy and usually quick.