I don't believe for a minute that this party was all about Jen. As I said, this birthday came on the heels of her cancer remission, which interfered with her bonding time with Zoey and Will. She has a lot to be thankful for, and I am glad she took this opportunity to let loose and celebrate! I don't remember her mentioning her cancer at the party at all. She is probably walking on a cloud that it appears she beat cancer and will be around to raise her children. However, being a physician, she is well aware that cancer can sometimes rear it's ugly head again, and life can be taken away so quickly, so good for her for mustering the energy to plan such a wonderful party. I had a dear friend "ring the bell" as Jen did after treatments, only to pass away 6 months later as it had returned, worse than before. Jen's positive attitude during this whole season has been amazing, and Will and Zoey hit the jackpot with parents. I don't remember one friend of mine ( myself included), that didn't make a big deal out of birthday parties starting with age 1. It's one party for the child a year, and I myself, enjoyed the heck out of planning and carrying them out. It certainly wasn't about me, but it was about how my husband and I loved our children, their friends, and wanting to celebrate a very special day -- in any way we saw fit.
If my granddaughter was bopping me with a balloon playfully, I would not give it a thought. That is not a precursor to hitting in the future. It was a new toy for her. Raising well balanced children takes patience, love, understanding, and the acceptance that you can only do your best. I found it better, as my children were growing, to pick my battles. I probably would have taken the balloon, rubbed it in Zoey's hair and show her how it sticks to a wall. It's a toy. Now, if she had been poking Bill in the face with the stick, intervention as to how exactly to play with the balloon would have been warranted, but she wasn't doing that.
Even if Jen never experienced cancer, she has every right, as a mom, to throw the best party she can for her child. She doesn't need a reason. And given the theme and activities, this party was clearly all about Will and he certainly seemed to have a great time. I applaud Jen for doing such a wonderful job when she is clearly not fully recovered from chemo.
In regards to favoritism, I see absolutely none. Will and Zoey are two very different children, at two different stages in life, and since Jen missed a chunk of time with Zoey while sick, they are still getting to know each other. They both have a lot of bonding left to do, especially since Zoey was not happy being left alone with Bill at first.