I think that leaving on Tuesday would be just right. I have had the experience of staying too short and too long. The first time I went to a CGW, I went for a week in July. Not many went to that particular CGW, and everyone had left by Tuesday morning. I was alone for the last two days of the trip

. In a typical workshop, about 1/2 leave on Sunday night or Monday morning.
When I went back in October, I left on early Monday morning, and I felt like I missed out on many activities taking place on Monday. When I went to SRW a couple of weeks ago, I went from Thursday afternoon to Monday night. This seemed to work well, as it matched up with most other attendees travel plans.
I think you have a good plan. Go for it! I hope this helps.
I look forward to meeting you in January. Unfortunately, my schedule around that time requires me to leave on Sunday right after the workshop.