I'd definitely pack light for what you bring with you on your bike, but there is no reason to pack light for the overnight in La Grange. The luggage service does all the work for you bringing it there, so you might as well pack everything you can.

Here is what I pack:
- Cycling clothes for Sunday
- Change of clothes for La Grange (some teams give you a t-shirt to wear when you arrive)
- Pajamas
- Toothbrush/toothpaste
- Body wash/shampoo/deodorant
- TOWEL (don't forget this!!!)
- Shower sandals
- Cot/pillow/sleeping bag (tent or air mattress depending on arrangements)
- Battery pack and phone charger (can buy at Best Buy for $70-$80, no power outlets in La Grange)