I'll admit up front that I have serious reservations about kids that young doing that much computer-based learning. Unschooling is of course very much child-led and interest-driven, but I think it's important that parents set up environments that encourage children to strike healthy balances. Fifty years ago your little intellectual might have been out in the natural world every day for hours, carrying a magnifying lens and field guides, collecting bugs and frogs and cataloging everything he finds -- active, social, creative, naturalistic types of activities. Today's culture and and the availability of technology have produced a situation where the same impulses to seek and learn have led him spend time with iPads and computers, in solitary, sedentary, more linear ways disconnected from the world at large.
My kids have many of the same impulses and have been drawn to the same sorts of things over the years. Technology so easily becomes the default activity -- always available, predictable, undemanding, diverting and requiring very little self-management skill or creativity. So I've tried to minimize its appeal.
I admit I've relaxed as my kids have grown into teens. But I see childhood as a precious window for creativity, play, the development of social connections and a holistic orientation to the world, so in order to promote those things I need to create an environment that values them. That, for me, has meant putting the precious bits of one-on-one time I have available with my kids into things that help create that balance. For instance I would not be spending a sibling's nap time helping such a child recognize states by shape using iPad apps. I'd be using that time for creative play, hands-on project-oriented things, reading aloud to him, art and music things. If I saw that he was typically lost in his electronic world while I was chatting and playing with his siblings, I would think about finding new ways to run the household and new ways to engage him ... perhaps by taking all of us out of the house for a daily walk along on a nature trail, or by asking for his help with meal preparation and other housework, or moving the computer to a less accessible area or limiting tech time to part of the day.
I think there's a danger in constantly feeding children with new interesting things to do. Some kids become novelty seekers and have trouble with aimlessness if others are not planning and filling their days. I think it's important that they learn to deal with fallow time by coming up with ideas for themselves. So perhaps what your ds needs most from you is a little bit of nothing ... the opportunity to have fallow time apart from his electronics, to discover the possibilities in conversation, chores, being out and about in the world, or simply alone with his thoughts.
I may be reading completely the wrong things into your post. If he is sociable and creative and active and contemplative and happy coming up with his own ideas for things to do, then you can ignore my cautionary thoughts. In general I would just encourage you to create an environment that is conducive to balance, and not to worry about where to lead him next ... just let him find his way by giving him opportunities to discover what's inside himself in terms of creative impulses, lateral connections, inspiration and interests.