No one's really addressed your gate check question:

Regional jets typically have less overhead then other aircraft, and standard carry-on roller bags won't fit into the overhead bins. On those flights, passengers must "gate check" (also called "valet check") their luggage. You get a tag from the gate agent and then leave the bag somewhere on the ramp as you board. When you disembark, the luggage is normally returned to you on the ramp, rather than at baggage claim.

Other airlines will offer to gate check baggage for you if overhead bins are full, but it's not a standard amenity on all airlines -- and I've never flown JetBlue or Virgin, so not sure of their policies. But I believe that neither of those airlines fly regional jets (and certainly not on cross-country flights), so it's unlikely you'll automatically be allowed to gate check your three big carry-ons for free.