I have been working on your answer! You did ask questions and a lot of good questions as well!
1. For your 5 yo: I would get the MMR now and then get the flu vaccines when all of you can get them. Since your 5 1/2 month old has to wait until 6 months anyway then all of you can get them at the same time. Hopefully that makes sense. ANd you are correct it has to be at least 4 weeks AFTER the MMR.
2. Get the injections instead of the nasal mists. There is a very weak but LIVE virus in the flu mist and it is VERY RARE that there is a transmission to another person but there has been cases of it so I would just eliminate that possibility and do the injections.
3. There is no good studies about nursing moms getting the vaccine and excretion in milk. It is advised just to use caution. However, that is why if you wait until he is over 6 months than you will be ok. There just is not a lot of information about that. Sorry.
4. As far as thimerosol free, it is difficult to get. Here is a site from the CDC that you can check out and see if the base will order for you. It is called FluZone.
This link is from the CDCs report on Prevention and Control of Influenza. The whole report is at:
Here's the part about vaccine without thimerosal:
Aventis Pasteur produces FluZone®, which is FDA-approved for persons aged >6 months. FluZone containing thimerosal as a preservative is available in multidose vials. Preservative-free FluZone packaged as 0.25-mL unit dose syringes is available for use among persons aged 6--35 months.
You can also find information at this site:
Questions & Answers: Thimerosal-Containing Influenza Vaccine
I hope that this helps you to make your decisions. I know that it is very confusing and a difficult choice. You are doing a great job and Thanks for serving our Country. My son is a Marine!