I'm glad you're excited about visiting Chicago - it's a great city. You'll be able to view all the Holiday decorations and maybe visit the Christkindl market while you're there, too. Yes, it can be cold, but it can also be quite nice. One year we still had roses on our bushes at Thanksgiving!

http://www.christkindlmarket.com/en/

Thanks razzledazzle, I'll definitely take that into consideration! Sounds fun :)

That looks beautiful Susan, will definitely be visiting the Christkindl market. I knew there was a reason Chicago had to stay :)

Thanks razzledazzle and Susan, both those suggestions are brilliant! Noted them both down :)

"I had a look and there's the amtrak but it says no checked baggage and we'll both have a suitcase with us. "

You are allowed to take baggage on Amtrak. You carry it with you and stow it in the racks near your seat. The "no checked baggage" statement means that the baggage is not taken away from you and stowed in some other place, like checked baggage on an airplane.

Thanks ellenem - will take our luggage along for the ride with us then.

We've booked a tent at Curry Village but they don't have a contact email so was wondering if anyone could help - will our suitcases be safe in our tent? Is there a lock on the door?

No checked baggage on an Amtrak train or bus means you are limited to a 50 lb. suitcase that you can put underneath on the bus or carry onto the train by yourself.
The San Joaquin trains north of Bakersfield tend to run quite close to the scheduled times. The YARTS bus from Merced to Yosemite waits for the passengers from the train.
The other option from the San Joaquin is to get off in Fresno and then taxi to the airport (FAT) to rent a car. From Fresno you go in through the south entrance and see Mariposa Grove first. I don't know how bad the view will be coming in from Merced after the Rim fire is out.