I bought the new Ravensburger version of this game at the end of 2016. We played the new rules a few times with my 6 and 7 year-olds, but found some annoyances (listed further down). I made some modifications that we all like - figured I'd share.
1) Each player starts with a secret treasure tile. If they find the tree with it, they reveal the tile, and take the tree. They then also take the face-up tile in the castle to be his/her new secret tile.
2) If a player lands on the horseshoe space by exact count, they can instantly go to the key space and guess where the castle treasure is.
3)Once a player successfully guesses the castle treasure tile, they are transported to the horseshoe space. They also take the tree instead of placing it back.
4) Instead of a race to three treasures, we play until there are no more castle tiles.
The best part about this variant, is that you can now will treasures without ever having to take the time heading to the castle. Also, my kid's have terrible poker faces, so you always new as soon as they saw the one for the castle. This way, if they find their secret one, they get the instant reward without spoiling anything.
The annoyances from the original rules:
1) Once someone guesses right on the key, they get to stay here and block the space, thus any players who lost the "race" cannot guess at the new card first.
2) Putting the trees back just made it tougher for the kids. They often revisted trees where the treasure was already gone.
Anyway, comment if you like, but I encourage you to try this variant if you are an adult playing with younger kids.
When my kids were younger we also played this game, removing the matching tree when collecting a treasure. Apart from that, we stayed with the original rules - my sons had good pokerfaces.