Depends how easily you get stressed. There's plenty of time throughout the year for studying anyway, just make sure you start earlier and you should be fine.
Overloading yourself isnt a great idea because you want to make sure that you get the highest grades possible in all your subjects, which can be difficult if you are doing too much. When you are 21 years old you wont care whether you took Higher French, but you'll certainly care if you messed up your academic career by getting bad grades.
Are you in a position where you could just study French outside school (not for a qualification, purely for fun), for example by attending language classes or taking private lessons? You dont need to be studying foreign languages academically in order to learn them; if you told your parents that you wanted to learn French/German in your spare time and asked for private lessons then they might be happy to provide them.