Activities with a 1 year old?

Hi everyone!

I live in Wakoshi (Saitama) and in summer I gonna have 8 (non consecutive) days off to spend alone with my daughter (11 months) and, even if she's young, I want to organize "expeditions" with her. Do you have place or activities to recommend for a Dad and his young kid in Tokyo (including Saitama)?

Thanks for your help!