My 5 year old and her 6 year old cousin loved looking for the letters and did recognize some of it. When it came to letters that are easily confused like the b, d, p, u, n, m, w, I drew lines underneath it to help them. This is especially great to practice those letters that can be reversed easily.
Collaboration was one thing they did too, helping to find all the rocks and matching them together. Even little one joined in!
You might want to see these posts too: