I don't feel like having dinner in front of the tv.
Why don't you want to have dinner tv time?
I just don't like this after school ritual, especially if it's food related.
It is ok that you do not want to participate in this plan. You should however let the others know that you wont be attending so if they do need to switch things up or make plans then they have time to.
I don't need to be in charge of telling everyone of my plans. I'm also going to leave.
That is up to you and how you feel about it in the end, I was just making a suggestion for you. You don't have to stick to any plan if it makes you uneasy.