What type lego for 3yo 9mths

[heartofhome]

My son doesn’t have any lego sets yet- just building blocks.
I have never bought lego yet as his sisters never had an interest.
Duplo is 3+ but think might be a bit too basic, and he won’t get long out of it- he is very able and past the stage of putting small parts in his mouth
But can’t really see a set or range that I think would be suitable?

If I were to buy lego friends set for 8.6yo and 6.5yo girls what is recommended also

Links would be appreciated

If you buy some duplo now, it is also compatible with the smaller lego when he moves onto it and using the different sizes together offers more flexibility. As long as it is the official Lego stuff it all fits together regardless of the size.