Does anyone know if it's okay to just charge both cells instead of balance charging? I don't know how to look up a two-cell balance charging IC for my 7.4V pack. I want to charge in circuit and it's just an rc battery. I can tap the 3 points for charging.
Using a so called 'balanced charger' will actively ensure that the two cells are equalized as well as charged charged up. Commercially built and sold 2-cell li batteries are made with cells closely matched to try and keep them close to being matched over their life even if not using a 'balanced charger', however it would be good for you to check periodically that the mid cell tap voltage is at 50% of the two cell output voltage.
For high performance, high current discharge packs I would say using a proper balance charger is a requirement for best results, safety, pack lifespan, etc.