I think...."Tell me about your holidays." is better.
I believe "Tell me your last holidays." is grammatically correct, but....
sounds strange to me at least....I don't know why.
Tell me what you did during your last holidays. OK to me.
Tell me your name. OK to me.
Tell me your last holidays. Not OK to me.
I'm not a native speaker, so please forgive me if I've made any mistakes.
Student or Learner