Just drive it till 5k, nothing to worry about.
The 6.6 qt sump for a 2.5L V6 is a lot of oil, if you look at clublexus.com and the UOA people did, most synthetic can go 15k and dino is good for 7.5-10k.
I think the 5k OCI is a safety margin for fuel dilution due to the direct injection. Because of the sump size and the 5k OCI, I'm just going to run the cheapest dino I can find (i.e. free oil from rebates) and call it a day.