I bought 16" MKW wheels for the winter at a car tuning shop. Someone had ordered them for his Grand Cherokee, but he changed his mind, so I had a good price for them and amazingly, they were fitting perfectly on the Journey. I'm not sure, but I think the wheels of the 2008+ Grand Caravan will fit. Otherwise, you can buy OEM 16" rims from the Journey SE.
For the tires, we have a lot of snow and ice here, in Canada during winter, so i bought Nokian Hakkapellitta 5 (studded) and they are amazing.