I have just bought my second Weeride.
I am now using with my second child, and my first child is still in the seat on his fathers bike at just over 4.
Not sure how the 2.8 year old below couldnt fit in, as my son is on 98%ile on NHS scale.
When I first bought I was worried about size as it looks small, but as the company give a money back guarantee if they dont fit at 4, I stuck with it.
And I was glad I did. Sizing is no issue and it is so much fun.
It attaches to the bike frame and not the handlebars so feels so much safer.
And I much prefer having my kids in front of me.
Its not cheap, but worth it for 3 years use.