Nils,
As someone who has to travel to observe, I can assure you it's a PITA. Of course your 5-10 min drive is better than my 45 minutes each way but packing up and unpacking the car will cost at least 30 minutes each way, probably more if you pack a thermos and snacks. Trust me, you will observe more often of you don't have to travel. If I was in your position I would look seriously at controlling the light in your yard and observe from there; I'm quite sure the sky overhead is quite dark once the local lighting is out of your eyes. If you can do that then scope portability become less of an issue and you can go for a bigger scope and/or a solid tube. A solid tube scope just being moved about the yard won't fall out of collimation too often so that also saves time.
If you do still want to travel at least do some preparatory work at home. I used to go out with my star atlas and red torch and just learn the naked-eye stars. That way my star hopping was much quicker when I was at a dark site. You can even set up the scope and practice finding object from home so you can quickly find them when you travel.
Don't believe anyone who says "x inches is big enough" -
nothing is big enough!
I've never heard anyone say "this scope gathers too much light" (OK - except when observing the moon but there are filters for that). Get as much aperture as you can.