Hi Loves,
My kids preferred educational computer games to work books. I think they learned a lot more from these than the books, plus the games were great for building logic and reasoning skills. (My personal philosophy is we learn far more when we're enjoying the process.) Some of their/my favorites were:
JumpStart 2nd (and beyond) Grade Adventures (general studies, reading, math)
Reader Rabbit (reading)
Operation Neptune (math -- goes up to pre-algebra)
Logical Journey of the Zoombinis (logic and critical thinking)
The Incredible Machine (spatial thinking, logic and critical thinking)
Dr. Brain (science, critical thinking)
Where in the World is Carmen Sandiego? (Geography)
Where in Time is Carmen Sandiego? (History)
Pajama Sam series (observation and problem solving)
Freddi Fish series (observation and problem solving)
You can find all of these on Amazon. Some of these games may be a little advanced for your son, but you can play with him and offer guidance. As an example, I bought the Sandiego, Dr. Brain, Operation Neptune, and the Zoombini's games for my son when he was 9, but my 5 yr-old daughter also loved them, even though I had to help her with a lot of the reading.
As fun and educational as the games are, I limited game time to 1 hour/day. During summer vacations, we spent a lot of time of hiking and exploring, poking into streams with water scopes, doing experiments of their choice and sometimes design based on the questions they asked (I'm a scientist, so I really encouraged this), building things, doing art/craft projects, visiting museums and aquariums, enjoying story time at the library, cooking, and playing board and card games. All of these activities build life and critical thinking skills. BTW, as far as board games go, it's hard to find really good ones in the stores anymore, but there are a lot of good ones on Amazon. Some of our favorites included: Constellation Station (astronomy), DinoHunt (paleontology), Junior Labyrinth, Labyrinth, and Master Labyrinth (in fact, just about any Ravensburger game or kit!). Scrabble and Boggle are great for learning spelling and vocabulary building. These were fun and educational for the entire family.