Since you have been only running three weeks I would take both Thursday and Friday off.  If you get antsy maybe you can go for a walk on Friday but make it at an easy pace.  You can maybe do some other form of exercise on Thursday, weights or ride a bike.  30 minutes for a 5K is very admirable especially if you haven't run in a while.  I didn't pick up running until about 8 months ago and I didn't break 30 minutes until four months into it.  I would have to add that I had a walking regimen going before I transitioned to running, and walking at a 14 minute mile pace.  It would be good if you can go online and download a 5K training plan, there are many free ones online.  These can help you vary your training so you can improve your endurance, and thus your time in a 5K.  Good luck in your 5K and way to go getting back into running.  It will definitely help you in your quest to lose weight.

I agree with resting for two full days before your 5K.  Also, I suggest you sip water all day Friday so you're well-hydrated on race morning.  I don't know the weather conditions where you are, but pre-hydration is even more important if it will be hot and/or humid.

I would concentrate on finishing well rather than trying for a specific time goal.  It's too easy to get caught up in the starting line excitement and start out too fast, only to be thoroughly winded after the first mile and having nothing left.  Time improvement will come with more training and learning to pace yourself.

Excellent, another Chicagoan in our midst.  I'm in McHenry.  I have heard of Loop the Lakes, but have never run it.  Saturday is now forecast to be mild, so you should have a good day.

If you're interested, our running club, Fox River Running Club, is hosting a 5K run/walk on May 22nd in partnership with Weight Watchers.  Go to our website, www.foxriverrunningclub.org, for details.