Add a couple links. I know you have some sitting in the bin. I jump from 25 to 28 all the time because it's sized for a 28. No other adjustment necessary.
I actually don't have any pins, though. I guess that I could run two quick links, but I'd rather not, though it's probably a non-issue.
I am getting close to EOL for these two chains, anyway, and I've learned from my mistake - I'll be sizing for a 28t on the next two, though I'll keep running the 12-25t 98% of the time.