Your freighters don´t sit in a parking swarm, they land on trains on Ceres. As Ceres is an airless world we needn´t concern ourselves with aerodynamic drag or entry stresses. Yet this is an incidental detail, as the point of using mass-driver trains to launch vessels it to free them to the Tyranny of the Rocket Equation . The Rocket Equation basically says one of three things. The vessel needs to be mostly fuel (current rockets), be efficient and horribly boring (ion drives) or be a torchship (which may fall under your restriction of "no super tech" and might be a bit on the dangerous side (Kzinti Lesson) ). The mass drivers are still a case for the Kzinti Lesson, but looking at Johns Law  that is unavoidable.
The mass drivers will be maglev trains  where vessels land on wagons and are pushed up to speed or slowed down. While this takes energy the energy isn´t fully lost if regenerative brakes  are used. To power the thing fusion would be nice but messing around with solar panels or fission plants would work, too. It matters that a lot of energy is needed. I´ll come back to that later. If you want to calculate the dimensions of the mass drivers this formula is relevant.
$v = d/\sqrt(d/(0,5*a))$
$v$ = velocity
$d$ = distance (track length)
$a$ = acceleration
$v$ should at least be at 510 $m/s$, as that is Ceres escape velocity. At the still human tolerable acceleration of 5 $g$ this gives you a track length of ca. 120 km. Play and plug as you like. It should be noted that the logical conclusion of this technology is a track around the equator, setting $d$ to infinite and allowing all kinds of funny high-velocity launching. Furthermore, this will allow Brachistochrone Orbitals  which are the opposite of our current Hohmann Transfers . A note on $a$, 5 $g$ seems to be the save human maximum but I would go for 3 $g$ as that is more comfortable. Unmanned vessels could be shot off at hundreds of $g$´s.
With the infrastructure of the spaceports cleared up let´s look at trajectories. Freighters will need to time their flight plans to the rotation of Ceres and need to maneuver to correct their courses in a manner allowing for save capture and beneficial departure. If both target and launch point have mass drivers only ion drives are needed for corrections. If not the mass drivers will still lower fuel demands and be economically viable, especially as using the power directly to launch vessels will be more efficient than producing Hydrogen Peroxide. (tell me in a comment should you want me to run the numbers). Hohman transfers will be dominant during the early phase of colonization, with Brachistochrone Orbitals only possible at certain times and only in the Belt. As mass-driver infrastructure improves the windows for Brachistochrone Orbitals will grow bigger until Hohman Trajectories will be a thing of the past like travel by horse is today. This obviously assumes that you don't have torchships.
As for your shuttle flight paths, there are two things I mentioned earlier that are relevant to this discussion. That running mass-driver takes a lot of energy and that according to you the colonisation of Ceres is in an early state. This leads to the conclusions that there will be few and short mass-drivers on Ceres. Around those the major settlements will grow but what about those far from these spaceports? Here your shuttle pilot comes in. He will pilot one of the many shuttles and thugs carrying people and materials to and from the mass-drivers. Now, why does this shuttle hopping happen? Ceres has a surface area of ca. 2.7 mil $m²$, roughly comparable to Kazakhstan. But the land is mountainous and the ice keeps melting and moving, so installing hyperloop trains  will take another century. Even roads are impractical.
As Ceres orbital speed at surface level is only 336 $m/s$ and the fuel is cheap the small vessels will fly extremely low trajectories, those who are risk-conscious a few kilometers high, those who want to cut cost only meters above the highest peaks. This is great story material as figuring out that there isn´t enough fuel to get you over the next mountain and pirates harpooning transport vessels down can create a lot of conflicts. The orbits would spread out like the canopy of a tree from the spaceports. it might be more accurate to call them "Jumps" because this isn't really different from jumping on Earth.
Finally, I would recommend the game "Kerbal Space Programm"  to you as it will allow you to get an intuitive understanding of orbital mechanics and delivers you the feel of being a spacefarer.