Absolutely. There is some text, but the game is an open information co-op, so everyone's hand is visible and you can work with and help each other. Most of the cues are not-textual. I think your son would have a blast with the game if he likes monsters, knights and that sort of thing. He'd have so many more decisions to make compared to Candy Land and other beginner kids games.
If he likes it, definitely get the Wizard's Tower. It makes the game much more fun. We didn't get Castle Panic until she was nine, but it was only because I wasn't aware of its existence until then.
Another game I played with my daughter when she was you son's age was Carcassonne. It has a lot of expansions that will keep you busy for a couple of years.
Good luck and have fun!
Actually it is a coop in an optional variant, normally it's a semi-coop - everybody loses together, but only one person wins. So per default rules no open information. No reason not play this way, but still, seems a lot of people forget it's not a full coop with default rules.