Loose parts are excellent materials for open-ended play. Saw a tree branch into pieces and you've got hours of engaging kids activities.
(In translation) 'Mooom, this is no wood. These aaaa haaaaystacks.'
It's been on for the whole summer: I give him anything in a form of a cylinder and look, it becomes a haystack. Just like this one.
And your toddlers, what is their fav activity this summer? - besides trucks & Co., off course :)