Ce que (vs ce qui) = what, which (relative pronouns)

The 2nd sentence is grammatically correct. The question relates to the whole idea of 'WHAT you do on the weekend' and this requires 'ce que' (followed by the subject pronoun in this case). Que cannot be used (none of its translations fit to give a meaningful sentence).

These related lessons should help clarify -

https://french.kwiziq.com/revision/grammar/when-to-use-que-to-say-whom-which-or-that-relative-pronouns

 

https://french.kwiziq.com/revision/grammar/ce-que-what-which-relative-pronouns