Your entry trailhead would be "Pohono Trail (Wawona Tunnel/ Bridalveil Fall parking)". I believe your exit would be "Pohono Trail (Glacier Point)", because the 4-Mile isn't part of any backcountry/overnight trek. You would be "exiting" at GP and then continuing (dayhiking?) on the 4-Mile.
Your exit trailhead and date aren't really important, quotas are based on your entry trailhead and date.
Keep in mind that you cannot camp on the Pohono east of the Bridalveil Creek crossing. Your most scenic camping probably is at Dewey Point, the closest camping on the Pohono to GP is the Bridalveil Creek crossing. And no camping on the 4-Mile either.
For transportation you could use the El Cap shuttle to Bridalveil Fall in the Valley then hike up to Tunnel View on the old Wawona Rd. When you finish the 4-Mile in the Valley there's a stop for the El Cap shuttle right there. The El Cap shuttle runs only in summer and is only about every 30 minutes or so.