I found on one project doing some animation that it was quicker and easier (if the path was generally straight line) to just use the Basic Animation Effect in L2, then use the Advanced Anim Effect for those with more complex paths or complex timings.
Anway, I agree that going from key to key to select is not that easy at present.
I can't seem to create new key frames for the second animated object without deleting or affecting the first object.
A key can be anywhere on the timeline and every change is a key for that object. Also, a key is not for one specific object, but all objects that have change. So if at timeline position 1 second you had selected and changed 3 car positions, then the timeline will show 1 key for all three cars. Selecting a car X at timeline 1 second (where the key/keyframe is), will let you change car X's keyframe but only car X, and so forth.
So if you are on a key that was there previously from a keyframe of a different object or you have moved the timeline, then simply selecting another object and changing its transforms will create a new key. So you don't have to be on a key to create a new keyframe.
If you want to have 2 objects changing at the same key, then so long as you have selected the key (ie moved the timeline over the key icon) then you just select which object you want to change. As above, the issue at present is always getting exactly to select that key, and sometimes you may end up being slightly off the current key and that results in creating a new key.
I think with playing around a little I have found that to get fairly accurate selection, using mouse, drag the timeline, then move the mouse down away from the timeline and drag, and it seems to (almost) click in place to the most current key.
More accuracy could be enabled by also allowing the max time to zoom into 1 seconds or even smaller steps. See what they come up with maybe in v2.1 if they have had a chance to look at things.
There's also an indicator provided (accidental I think), but use with care. To see if you are on a key and an object has a keyframe at that key, place or move your mouse over the Remove Key icon, you should notice that the object icon flashes a red dot, so that means it has a key, an other objects that do not have a keyframe at that key will not have a flashing red dot, then its just a matter of getting the timeline selection for that key (as above).
Not sure on the right track for you, but hope the above may help in a small way.