If you decide to go the route of discreet pumping in public area, I would suggest using [https://www.amazon.com/Freemie-Collection-Cups-Concealable-Funnels/dp/B00UV6JDN8](Freemie) cups and quiet battery operated electric pump. The freemies can be worn under a loose fitting shirt with just a couple of thin tubes going to the pump.
Keep the breastmilk. You don't need a fridge, an ice pack will keep it cool.
The spectra is awesome for travel, however that is the one that needs adapter pieces to use the Medela parts. The bottle the spectra is set to pump into is a wide mouth. The Avent, and Dr Browns bottles will fit straight onto the Medela as it uses standard mouth sizes.
The pumping cones for the medela are the ones that fit most handsfree bra's, and quite frankly most common items will fit the medela. However you can order adapter kits off Amazon for the Spectra to use the Medela phlanges easily.
Flanges should be the size of your areola, and this is something they can help go over with you in the hospital.
I am using The Frremie collection cups with the Spectra. I love them as they go under my clothes, and really easy to clean.
If you want I can take photos of the different set ups that I use if you think that would help.
I bought the Freemie's (Freemie Collection Cups The Only Hands Free and Concealable Breast Pump Milk Collection System, Clear, 25/28 mm Funnels https://www.amazon.com/dp/B00UV6JDN8/ref=cm_sw_r_cp_api_1E-Eyb8Z7YA2B) when I went back to work (and a 9 volt car adapter for my pump) and they work sooo much better than my pumping bra. They don't stick out so I don't knock them while driving. I like to put it all together once I'm in the car and have my seat belt in, so I can get into a comfortable position. I don't see it being a problem with shifting, as long as you have the tubing out of the way before driving. I also got extra long tubing so I could maneuver it behind my shoulder to keep it in place.
Freemies have sped up my pump time substantially. No need for a pumping bra since they tuck right in to your regular bra. And I don't think pumping only 5 ounces each time should lower your supply since your body makes what it is used to using up. (So, if you are usually pumping 15 ounces it will keep making 15 ounces.) I actually cut out a pumping session at work and just pump a little longer instead. Would that be an option for you? I go 4+ hours between sessions with no issues with my afternoon supply. (I had issues when my pump broke, but that's another story.)
My little dude has all sorts of eating problems (tongue tie, really inefficient, etc). So my current routine is to breastfeed him and then bottle feed him while pumping. I use what I pumped the day before to supplement him while I'm pumping. I bought these things so I could be hands (and weird things hanging off my chest) free while I feed/pump simultaneously. Kind of pricey, but really worth it: http://www.amazon.com/Freemie-Collection-Cups-Concealable-Funnels/dp/B00UV6JDN8/ref=sr_1_1_a_it?ie=UTF8&qid=1464114081&sr=8-1&keywords=freemies
These work very well to just slip into your bra cups. however practice with them first, if you use them incorrectly they will leak! https://www.amazon.com/dp/B00UV6JDN8/ref=cm_sw_r_cp_apa_Z8xRBbAFN7ET8
Freemies!!. And Medela Freestyle??
I think these are the ones used https://www.amazon.com/Freemie-Breast-Collection-System-Clear/dp/B00UV6JDN8/