Haha, don't worry about it, it's fine. Just as a rule of thumb, if you want to make it a pony song, make sure that it's related to ponies and you explain how it's related if it's not completely obvious. If it had to be happy and cute to be pony related, then we wouldn't consider "Nightmare Night" by Glaze pony related

Throwing pony onto the wallpaper or title or just slapping pony samples on a song simply to make it pony related is one of the 7 deadly sins. If you can't find a reason to relate it to ponies, don't put ponies on it. And don't worry about posting a mixture of pony and nonpony songs, people will subscribe to your music if they like you, and if they unsub because they hate ponies, then just don't worry about it, bigoted idiots aren't the people you would want associating with you anyways, lol.