I agree with AlphaZeta. C++ is a wonderful language--for desktop computers. IMO it does not belong in embedded systems (such as arduino). The reason is that C++ can enable some bad behavior (by inexperienced programmers). C is more rigid (and smaller).
Also there is less syntax in C than C++. C++ contains some very nice syntax but it can be seemingly irregular to new programmers and can be confusing.
As someone who has taught C++ as a first language to college freshmen I can with some confidence say that while it has probably the most long term utility to a programmer it's not a great first language.
Besides C++ was originally an extension of C (and still mostly is/should be) so anything you learn in C counts in C++ when you want to learn that later