Shih Tzus

Hello! My parents have a 1 1/2 year old Shih Tzu, Lucy. She was bred twice starting on January 2 with 24 hours between and is due in between March 2 and 7. Between my parents and I, there will be 2 of us there at all times during that week. And of course cell phones ready.
I will admit inpregnating her was a bit of a whim on my parents part but since then I have been doing quite as much research as I can (all internet based). I've convinced them to bring her to the vet (first appointment this Saturday). If I had known what I know now, I would have convinced them to wait until her next heat (so she would be 2) and so that more research could have been done.
We've switched her to puppy food. She's not a big fan of cottage cheese, so we give her a spoonful of peanut butter. We've made her a whelping box in the laundry room (where she already slept). We've also collected items for the actual labour (e.g. plastic sheets, lots of towels, thread, snot-sucker, etc). And of course, we give her lots of love and tummy rubs.
Both of Lucy's parents were quite small and they birthed 6 puppies, including our own Lucy. Lucy's mate was also quite small. I am very concerned for her as her tummy is already big and she has 1 to 2 weeks left to go!
I guess my question is, what else can I do? Are there any more suggestions that avid breeders may have for me? I've read about many complications and feel prepared but I know that something may happen that I have no idea about. Please, any advice from experienced people would be appreciated!
We love our Lucy and even though we acted stupidly and rashley, I am hoping that everything will go okay. Is there anything else I need to know for the big day?
Also, one of the puppies (preferably a girl) will go home with me once weened. I'm thinking Chloe? Bella? Laela? Any other thoughts?

I'm also wondering what I should expect after the puppies come? For Lucy and the puppies. I'm a bit sketchy on that. Any advice welcome.

Thank you! Very helpful!

Great! We'll try that! Thanks for the advice!