I would recommend a coal tar type sealer. It seems that the coal tar is a longer lasting product than the other two listed. You do not necessarily have to do it on a hot day, as a matter a fact the fumes given off from the sealer can cause a fair skinned person to burn really easy if you are not used to working with this stuff. You do have to make sure that it is not going to frost on the night you will be applying it as that will make it flake off through out the winter.
The very best way to put sealer down is with a push broom. One thing a squeegee will do is make the surface really slick when it gets wet. That why we don't like to use them, the drive can become a falling hazard especially for the elderly.
As far as letting asphalt breath; well that is total nonsense. If ya wanted it to breath then ya wouldn't bother with compacting it. There is nothing there to breath.
What the sealer does is it prevents moister from getting into the small voids. This is really important in cold weather. If moister does penetrate the blacktop then when it freezes the moister expands leading to premature failure of the pavement.
If you do have cracks in the driveway all you need to do is, take some of your sealer add some silica sand to it to form a paste. Take the paste and apply it with a margin trowel to a smooth finish. You will want to do this a day before you plan on sealing the drive.
