This is a simple activity you can do with big or small legos. I used the same number sheets we used in the Domino Counting activity so this was really a "no prep" activity for us.
Counting (one-to-one correspondence)
Missing Addend (Some kids may be able to say "I have 5 legos, I need 2 more to make a stack of 7."
My daughter loved being able to see that 7 was taller than 4! This was an easy way to talk about more and less.
She also loved making different types of towers for each stack....long towers, chunky towers, and skinny towers like this one: