I don't want to plan a second baby shower
I don't know why you want to go against local tradition.
I don't want to be involved.
If someone is having a baby, you should be there for them. It's wrong to ditch their baby shower.
I don't want to plan it, perform it or anything.
I guess if you're that adamant about not doing another one then no one should force you. You should tell the person as soon as you can that you're not doing the baby shower. They would need a new person quickly.