I would consider concentrating on the three R's so to speak- reading, writing (spelling, handwriting, grammar), and math in gentle way since he is still 4 grin When my son was 4, he hated writing. You could experiment with chalkboards, white boards, and try HWT for 10 minutes a day. If he is up to it, then you could try things orally for a while till his writing gets up to speed which may take a couple of years as it did in my ds.

I did this and am doing this with my ds who is about to turn 8. He sounds like your son in many ways and yes, he loves science. We do some science with his cyber school, but I do not place a heavy emphasis on this since he learns oodles about science in his free time on his own wink. Of course, in the next couple of years, I will have him focus more on science future, but right now he does fantastic with all of the reading he does in his spare time. I would just supply him with numerous science books for his spare reading and see what happens grin.

I think that by concentrating on the 3 R's, then it will be easier to expand his studies and activities IMHO.

At this age, you may want to consider foreign language though since kid's brains just soak up languages especially between 4-7 years of age grin I use Muzzy Spanish and Muzzy german. There are many great foreign language programs for young kids.