I need help painting an acrylic chair!

Hi. I was hoping someone could help me. My client wants to use this chair for her daughter's bat mitzvah. I'm going to paint the back of the chair using acrylic paints, but she would also like people to write their names on it as well. Do you think paint markers (Sharpie oil pens), regular sharpies or felt paint markers would work? Or do you think I should do a clear coat of varnish first before they sign and then a second coat after? If you know of a good varnish that would also be helpful. I have never painted on acrylic. Any help or recommendations would be most helpful!

Thank you,
The acrylic chair.
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