And lucky you being in Baltimore!
To answer your question - I think ER would be your best choice to start. Then you can get some ICU experience (trauma ICU then CVICU would be ideal!). Some may disagree (and that is okay, too!) but IMHO I think it easier to transition to the ICU from the ED. ICU nurses have a tougher time going to the ED than vice versa! (The devil is in the details!)
There are advantages/disadvantages to any location - I would think that if you can make it in the Adult ED at Hopkins or UMBC RCA you will be fine anywhere. I would not get pedes speciality unless you plan on speciality practice.
An ideal flight nurse - 3 years general ED (Level 1 a plus).
A year+ each of Trauma ICU, CV ICU, High Risk OB, Peds, Education.
As for your flight goal - check with the education folks at Maryland Express Care and see if they can give you some details on their program & staff requirements. In order to eat an elephant, you have to take one bite at a time!