A number of plants (often unrelated) are commonly known as "Creeping Charlie" so it would depend on which one you are interested in buying. In many places, certain species commonly known as Creeping Charlie are considered a noxious, invasive weed. If kept in the house you're probably ok, but in your yard, many communities will make you spray to kill it. You probably want Plectranthus.australis, which is known as both Swedish Ivy, and/or Creeping Charlie, however even that is invasive in some. Contact your local Extension Agent to find out which species is allowed in your location. They should be able to recommend a source to acquire permited species.
You should still be weeks away from frost, and even longer to a hard freeze. In addition, English Ivy is a rather tough plant. Planting them now would be fine. Plant them, water well several times so they are moist going into winter, and mulch with a bit of straw, pine straw, or such. They will be fine.
Holes should be about 1.5 feet apart, and roughly 2 inches deep. English Ivy is a rapid grower - so much so that in places its considered an invasive weed - so it will spread and fill in the gaps.
You can plant this after last frost in spring when rain will help provide regular watering to get it established.
Yes you can train these to climb a wall. BUT, it is best if it is a brick or stone wall. The little tendrils the plant has that enable it to cling to a wall are very hard on wooden surfaces and will damage or destroy them.
Mine came in plastic containers. Probably all of them will.
Each plant has a mature coverage possibility of 72 x 72 inches.
The length of the vines can vary a lot throughout the year from 6 inches to 14 inches. Each plant is grown in an individual 3 1/4 in. square pot.