You will need to “sell” your decision to your parents. One of the paramount principles of salesmanship is not to denigrate the “competition” but rather acknowledge the worth of the competing product, and then gently and charitably, show how the product you offer is better, has more features, is more “friendly”. This tactic validates your prospects historical decisions and is not in any way adversarial. I think this is something to keep in mind when broaching the subject to your parents. Let them know that there is much good that they have “taught” you, but there is something in the RCC that you find is more enriching in your spiritual growth and journey. Something that speaks to you, that brings you closer to Christ.
Be prepared for all the standard arguments, but be firm in your decision, and loving toward your parents. Know that they will feel it a betrayal initially, but over time with charity and love toward your parents, they will probably come to some peace about it.
Remember Jesus said he did not come to bring peace … a father will oppose his son, a mother, her daughter. But in the end, with prayer, love, and charity, have faith the Lord will work it out.