We are doing a family reunion in late june up at the point, so we're going to upgrade our season passes from gold to platinum.  Since we've made that commitment, we now plan to head down to Carowinds in late march to take in that park, however the processing at KI doesn't start until April, what is the best way to upgrade our passes prior to Carowinds?  Just do it when we get there, could be a nightmare since that is their 2nd weekend and I'm sure the ticket lines will be longer with other people looking to purchase a pass/renew/etc...

I would call CS up at CP and see if it can be done over the phone. 

I upgraded our passes from gold to platinum this winter, about a month ago now. I used to Kings Island website and didn't have any issues processing them and have all the Apps updated and ready to go. I downloaded the app of each park that I plan on visiting and it shows platinum passes for all my family. So I don't think you should have any issues with them being processed if you do it online. 

thanks for the info

Just to add, you can only do it online if you haven't renewed for 2020 yet, in which case you could simply renew as platinum and exchange your pass ID card on your first visit.

Otherwise, Guest Services at Carowinds should be able to upgrade your pass, but I would recommend getting there early to beat the crowd. If you're staying at one of the nearby hotels, you might choose to walk over instead of waiting on the parking lot to open. @pianoman did this a few years ago, but it took awhile for Guest Services to figure it out.