One of the most difficult things with a diagnosis like this, beyond the initial shock, is the toll the treatments take on you over time. So she'll probably get a lot of offers and gifts up front, but the treatments will tend to sap her strength over time. So, while your support is wonderful now, it's going to be more important down the road.
One of the best things we've done with several people who've had critical illnesses is to start a network of helpers. It's very hard for the ill person to organize and decide what's needed and then ask people and coordinate a schedule. It's exhausting. The person does not need one more thing to do. Yes, she will probably need help with meals, but right now it's hard to know what will appeal to her - so gift cards for meals might be premature, and might be the wrong thing.
We found a useful website called Lotsa Helping Hands - it's free. I also found their customer support to be excellent. The person in need can designate a couple of coordinators, who then sends the newsletter invitation out to their circles of influence. So your kid's teacher could select someone from the school or the class, and perhaps someone from her family or group of personal friends. They would organize with her what she needs/wants, and put it on line in a newsletter that ONLY goes to those invited to join. So, for example, one friend of ours needed meals 4 days a week - she chose what she wanted and didn't want, and that could change based on her tastes. We put a cooler outside her garage, and people signed up for the days they wanted, and listed what they were bringing. The next person to sign up could see that lasagna and salad were already listed for Monday, so they could avoid making something similar on Wednesday. Everyone could see the listing that they didn't like pork and that there was a nut allergy in the family, for example. Things like "disposable containers" were specified so there was no need to keep track of dishes to return.
As time went on for another friend, it became important to sign up to drive her to appointments and to pick up her kids for softball or karate on certain days. So the coordinators just listed those tasks and the necessary days, and people signed up.
The person in need (or their family member, whoever is handling things) gets an email every day about what's been signed up for and by whom, so they know who's picking up the kids or who's bringing dinner. It also kept a list for her and let her send out thank you notes when it was all over.
I think the best thing you could do would be to find out who on the school staff is closest to her, and organize a meeting to discuss how best to channel all the well-wishers' offers of help so that this teacher gets what she needs when she needs it, and isn't overwhelmed by keeping track of who did what and who needs to be thanked.
That's not to say that the ideas of a bead kit or books are bad - they aren't. I agree with you that flowers are overdone - they also die and can be more depressing for the patient than uplifting. But organizing a chain of people to pitch in can be so encouraging to the patient and let them know that so many people are pulling for her - that can be the greatest gift of all.