I was wondering if Yogananda’s teachings would fall under the Vedanta Philosophy?
Or is Kriya Yoga something separate?
No, Kriya Yoga is not something separate. But nor it is not pure Vedanta: only partially Vedanta. Here is what I mean: Among the six darshanas (Sankhya, Yoga, Vedanta, Nyaya, Mimansa, Vaisesika) Yogananda gave importance to the first three: Sankhya, Yoga, Vedanta, stating that the path of Kriya Yoga (earlier called "Yogoda") is based on these three ancient philosophies. Here are his words:
"Yogoda, or Self-Realization doctrine, teaches the combined technique of Self-Realization as taught in Sankhya, Yoga and Vedanta – and is based on the universal, usable principles underlying all religions."
Later he gave a more detailed explanation, why our path represents these three darshanas (systems of philosophy):
"Of the six principal systems of Hindu philosophy, Sankhya expounds the why of religion, Vedanta describes the end to be attained, and Yoga provides the method for that attainment. Together, these concepts constitute true religion, whose twofold purpose is to show man how to avoid suffering and how to contact the bliss of the Supreme One."
If you are of philosophical nature and want to deepen your understanding of Sankhya, I recommend Sri Yukteswar’s The Holy Science, chapter 1, in which he explains the 24 principles of creation: the basic concept of Shankhya.
To deepen the darshana "Yoga" (referring to the Yoga Sutras) I recommend Swami Kriyananda’s new book, Yoga Sutras (Aphorisms) of Patanjali, which he has just finished. It should be published soon.
To get a deep and intuitive understanding of Vedanta, you may meditate on Yogananda’s poem "Samadhi," from his Autobiography of a Yogi.
Swami Kriyananda has also published a very helpful book, The Essence of Self-Realization, presenting quotes of Yogananda. He explained that he structured the book in a specific way: the first part of it is Sankhya (The Folly of Materialism etc.); the second part is Yoga (how to go about the path to God); the third part is Vedanta (what happens when Self-realization is achieved). It is wonderful spiritual literature and perfectly represents the path of Kriya Yoga.
God bless you, jayadev