Hi, My family and I are military AND visit WDW regularly in January.
1. SOG is nice, but it is NOT the cheapest or best deal. The room sizes are big but we find we prefer the POP. Check out
www.mousesavers.com for the latest discount codes. Typically we get a room at pop for under 60 per night.
SOG has the perk of being able to walk to the Polynesian (sp?) AND the TTC.
2. Tickets, Military tickets, plus staying at a value resort is usually the cheapest (but always double check).
**HOWEVER, if you can get a discounted package deal from WDW with food (even quick service), hotel (value resort), and tickets, it tends to be cheaper than food (OOP, plus military tickets, plus pop) - this would be like buy 4, stay for 3 more free/ free dining, etc.. Again, always see what your needs are and estimate your costs and see if it works for you to be cheaper.
3. Weather, every-time we have have gone in January the weather has always been a mixed bag. It could be shorts weather in the day and , jean and jacket weather at night. One year we even needed our gloves, scarf, and hat every night. REMEMBER, a 50 degree night might seem warm during the winter, but when it is 80 during the day, the 50 feels VERY cold. My best advice is to bring a hat (for the ears), scarf, and gloves. Also bring a lightweight jacket. We found capris worked best for the girls and thin pants for the boys (or long shorts). Be prepared for anything!! Bring your rain poncho as well. That rain gets COLD in January.
4. Crowds .... as long as school is in session, it will mostly likely be an enjoyable crowd level. January tends to be a slow time of the year anyways. The marathon is a big pain to deal with if you have reservations. I would skip making them this day unless it is later in the day. My experience is the day or two after the marathon lightens up in the crowd, but even with the marathon it doesn't seem that bad IMHO.
5. count on Splash Mountain being closed for refurbishment. I have yet to go in January and it is open.
6. I love going in January and try to whenever I can.
7. HAVE FFFFFUUUUUUNNNNNNN
** The above is all based on my experience (gone 6 times in Jan) and all made in my honest opinion.