My tank runs at 78-79 F which is not much higher and my cards have thrived. Best be ready to crank up the temps to treat ich if it comes along though (I did that twice in 2 years----to 86F). If you cannot go any higher than 25C no matter what I'd think twice.
I have some Potamogeton species that supposedly only like cooler water but they've done fine for me warmer than they supposedly like. Which ones in particular do you have that you fear cannot tolerate a few degrees warmer?