Compared to the other children, Nami's child has very high strengths. In fact, he apparently has the potential to become anything aside from an athlete (which I'm sure he can become anyway with some pushing.) Like Nami, he seems to be a thinker: learning and art are his especially good traits.
In order to make up for his strengths, he unfortunately doesn't actually seem to be interested in much. He has a high potential to become an artist or a farmer, however. It shouldn't be too hard raising his interests in other areas, as most of his strengths are high.
Stages of Life
Note: Your child's personality will differ according to how you've raised him, meaning that your child will not necessarily turn out as listed here. This data is based off of Akie's own experience in the game.
Toddler Stage (chapter 2)
Three words could describe him: perfect little angel. He is so well-bahaved and calm compared to the other two. He might eventually start protesting when bedtime comes, but that's only if you've been giving him too much attention. Nami isn't even in the room half the time when his bedtime comes, and if she's not, he will always go to bed by himself!
He's obsessed with shapes and colors. He'll often ask you if you are... square. While you aren't exactly square, you can either tell him you are or you are not (though he'll be rather disappointed if you tell him you're not.) He eventually also developed a fondness for plants.
This little guy does go outside some, but not that often. And when he does, he rarely goes farther than the toolshed. He seems to be very unlike his mother in this way, but I'm supposing that his unsociable nature and love for learning were inherited from Nami's side.
Boyhood Stage (chapter 3)
He's still shy and well-behaved, but does go out a lot. He'll hang around Cody's house or other areas all day.
He's quite interested in art, and really seems to look up to Cody. He'll often ask you what you think that... thing is by Cody's house. (I'm not sure what he's referring to.) Cody isn't the only person whom he talked about: just like his mother, he seems to enjoy observing people in their daily business without actually playing much of a part in other people's lives.
He likes eggs, milk, and seeds.
Teenage Stage (chapter 4)
The teenage years are the hardest point in anyone's life, so your child is no exception. Though he might not resent you too much, Nami's child will find almost everything his mother does as annoying. (He probably doesn't realize that as far as his personality goes, he is very much like his mother!) On top of that, he's fairly depressed much of the time, even telling you he thinks he would have preferred to have never been born. However, he still has an interest in both plants and animals.
Nami and Carter seem to think he will grow up to be an archeologist... I'm not exactly sure where that idea came from.
He likes tomatoes and goat's milk now.
Adult Stage (chapters 5 & 6)
He's not nearly as depressed as he was as a teenager, but he's not exactly the cheerful, happy-go-lucky type either (just like his mother.) He has decided, though, that he wants to take over the farm, and that's exactly what he did, concentrating on plant care and getting rid of that pesky mole cricket...
He still liked tomatoes and goat's milk.