S.,
I just wanted to chime in with some information about your son changing the first letter of each word to "L" or "R." This is a very common thing for children to do, especially as they are getting ready to learn to read. It shows that he is understanding how words break down into phonemic sounds. Most children play this game with songs, but some children just speak that way. If you play that game with a song, then you get to sing along, too and it is fun! Playing with language is a wonderful thing!
Here is a suggestion. We play this game a lot while we are driving.
Me "Say the word ball."
Kids "Ball."
Me "Take away the b."
Kids "All."
Me "Add a w (or I'll say the w sound) to the beginning."
Kids "Wall."
This can be played with real or nonsense words and kids love it especially when you make a string of words. We play a lot of question and answer games driving in the car to keep the kids busy. Work on phonemic awareness and math word stories.
Also, does your son enjoy radio theatre? I'm not talking about books on tape; I'm thinking about acting on the radio or on CD. Something like Adventures in Oydssey where kids have to really pay attention and create the story in their minds is very good for kids with higher level thinking abilities.
I also just want to encourage you that sometimes all kids get cranky and negative. When ourkids are struggling with this, we go around the dinner table and everyone has to answer the question, "What are the three best things that happened to you today?" It gets the conversation going in a positive direction and everyone gets a turn so they feel special.
If in his imagination, the building is the Star Ship Enterprise, then let it be the Star Ship Enterprise. You cannot argue with a child's imagination. I know he was arguing with his little brother, so all you have to say to the little brother is not to argue and for today the building is... whatever he is imagining it is. Don't turn this into a big deal or a big debate. As the saying goes, "Choose the hills you are willing to die on."
I know you said that you have a lot of educational computer games. I didn't read all of your responses. Have you tried Freddi Fish, Pajama Sam or Spy Fox games yet? These are wonderful adventure games of logic. I would start with Freddi Fish and work your way up to the harder ones like Spy Fox. You can find them on ebay or Amazon or in a store. We also like Reader Rabbit because the games automatically switch to the level your child is performing. Look for the A.D.A.P.T learning technology games.
Marble runs are good as well as anything he has to design and build himself. Even though he is not reading, word searches are good as well as books like Where's Waldo where you have to find the hidden images. I'm just brainstorming now on what my little guy liked when he was four. He is six now and in first grade, but has always been good with numbers especially when it had to do with sports. Children who think mathematically usually also do well with visioning space and the use of it. They enjoying building huts out of blankets and spaceships out of boxes. (All kids love this, but mathematical thinkers think differently about these things and can compute in their minds what they will need and how it will look before they get started. It is amazing if you can get him to verbalize what is going on in his head.)
Take what he likes to do now and expand on it. Our son likes sports, so all of his math questions tend to center around sports. I also agree that you need to keep him active, not just busy. I hope all of my babbling is helpful!
Theresa