I'm so sorry your family has to deal with it. I know that they usually check to see if the leukemia has spread to the spinal column. If it has then it's usually not a great sign. The problem with leukemia is that the cancer has already spread throughout the entire body. Like a lymphomatic cancer. I don't know where the bump is, but it could possibly be a lymph node that has swollen to a gigantic size. If it is a lymph node it probably is the leukemia, it will decrease in size and disappear within a week or two of chemotherapy being started. If it isn't a lymph node, then I honestly don't know what to tell you, just many hugs and thoughts and prayers going your way.
I would suggest getting the book "Childhood Leukemia: A guide for Families, Friends and Caregivers" by Nancy L Keene. It is heavy reading, but really a must to understanding what leukemia is and isn't, plus it goes into all the different types of treatment, the different drugs in the chemotherapy, side effects, ect ect.
Before deciding on how they will treat her though, they will have to figure out if it is AML or ALL. As soon as they know that, they will start the chemotherapy that day. Or the day after. Have they placed a central line or Broviac yet? For that she will have to undergo surgery to place either one. A central line is a lot easier as then the Broviac to deal with but they are essentially the same thing. They get rid of the need for the children to have an IV in their arm. Plus it gets rid of all the daily/weekly need for needles as they can get blood straight from the Brovi or CL. It is basically a tube that is inserted into the vein or artery near the heart.
I'm trying to remember what else they did right at the beginning. There was echocardigrams, CT scans, many pokes and needles.
I don't know if this will put your mind at ease or not, but in regards to the chemo. Usually they pump the little kids full of anti naseau medication ect, so some kids aren't sick from the chemo, some still react though. The hair usually takes 2-3-4 weeks after chemo starts to fall out. Chemo itself is carcengenic so for your little ones I would suggest that they not be in the room while little K is recieving chemo.
Thinking of you lots today.