Legos & Legos duplo (10029 Harlem)

Hi I'm looking for legos and lego duplos for my six-year-old and my toddler so that they can play legos together. my son loves legos and he has a few but the they're too small for him to play with his sister. so I was hoping that somebody either had some lego duplos that they were looking to donate or give away and also regular legos for him because he is a master builder. anything would help I'm willing to travel thank you