CONGRATULATIONS!
Neptune would need to be in that part of a fixed sign rather than a mutable to be significantly aspected to the Sun/Moon midpoint - I was using a 30 degree graphic ephemeris and must have got confused about the signs. But some people really struggle with that contact.
One thing that occurs to me about the synchronicity around this birth is that I didn't see the post in which you first mention the possibility of the 5th of Feb until you had already posted to say you were off to the hospital. I would have suggested that you consider going for the 5th of Feb because the Moon moves into Taurus and sextiles the Mercury Neptune conjunction. Its not that the 5th Feb aspects are better than those for the 4th. One advantage of the 5th is the excellent element balance, which is very rare. On the 5th there was a lack of fire, which could be noticeable given that the Sun is in Aquarius and making only wide aspects, Saturn is in the 5th house, and Mars is in Libra.
Its a very dynamic chart. Because all of the trines are very wide, one of the strongest themes is the predominance of dynamic aspects compared to flowing aspects. Perhaps this is one of the most important things to consider as you nurture your son into adulthood. Dynamic charts show ability to achieve much in terms of personal growth and worldly success, but conscious effort is needed to get all of the energies working together. Since so much projection occurs in early life, you can model positive ways of integrating the functions which are in dynamic aspect to one another.
Jupiter rising in Cancer is a lovely placement to have, and it puts the other t square planets in angular houses too. This is good, because it helps the energies of the t square to be expressed in the dynamic way that suits this type of configuration. Try to get him to embrace his Venus Pluto energy, and to find increasingly rewarding ways to live it. This will help him to get more out of relationships as he gets older.
As Billsim92 noticed, the Sun had arrived within a wide square to Saturn by the 4th. Interestingly, this aspect will be exact by secondary progression around the age of 7. This is always a significant time in a child's life, and if you want to read more about this then Rudolph Steiner and Bruno Bettelheim are both very insightful. It is always a significant age because transiting Saturn squares its natal position, and the progressed Moon squares its natal position also. In your son's case, the progressed Sun will also square natal Saturn, and transiting Saturn will conjunct the progressed Sun. So a very important time ripe with the potential to get him in touch with that widely aspected 8th house Aquarian Sun. Around this time, transiting Uranus may also be in semisquare and sesquiquadrate aspects to the t square planets.
With regard to the Sun, you could reflect on the strength of yours and the father's sense of identity - perhaps especially the father. By allowing yourselves to shine as individuals, you act as role models for your son's own ability to shine his unique light into the world.
He will also need to feel safe to express emotions as they arise, though of course he'll need the usual guidance and boundaries.
There may be lots of questions about spirituality and religion at some point. This will probably be an important feature in his life in one way or another due to the 9th house emphasis which involves Pisces and Neptune. His mind will be drawn to the bigger picture always, and he will tend to organise his thoughts in terms of some spiritual perspective. Although it doesn't show up on the chart, Chiron offers a flowing channel for the release of the tension inherent in Jupiter opposite Venus Pluto. There is a sense that he will be keen to use his dynamic energy to help others in accord with some kind of religious/spiritual belief, especially since the trine is to the first house Jupiter. Jupiter and asc are both ruled by Moon in Aries, which instinctively seeks a cause to fight for.
All in all, he has the markings of a very creative individual who will make a big difference to the lives of many of the people he comes into contact with.