I'm noticing that the written English in your post is just fine, aside from one missing article. I don't have any information about your spoken English comfort, though, and that is a piece of the equation to consider for yourself.
My family has some experience with the multiple language household, so I will share my thoughts and experiences.
My husband is not from the United States; I am, however I met him in his home country (Tanzania) and our relationship was established in Swahili, the national language of Tanzania. I'm reasonably fluent, though I'm definitely more fluent in English, especially in talking about emotional or relationship topics. It is very important to us that our children be able to speak Swahili, so they can communicate with their relatives on his side. We therefore chose to speak only Swahili in the home to give them a strong basis in that language. My mother was worried that our kids wouldn't learn English well, however I figured there would be no problem with them learning English because everything outside the home and the media (tv, radio, movies, most books, etc) would be in English, so they would naturally pick it up. The real challenge would be to maintain their ability to speak Swahili, and indeed that is what has happened. They speak, read, and write English just fine; it has sometimes been a real struggle to keep their Swahili language fluency up, though trips for 2 months every other summer to Tanzania have definitely helped. Our experiences resemble what I have read about immigrant families, where the parents would speak to the kids in the home country language and the kids would answer in English--the children could understand the home country language, but did not speak it. If you want your kids to continue to be able to speak Chinese, I think you will need to maintain Chinese as the main language of your home (and create opportunities for them to be in a Chinese-language environment outside the home whenever possible).
The down side...I will say that I think my husband has not developed as much English language proficiency as he would have if we were using English in the home, so there has been a cost. We think it's worth it, though, because our kids can stay connected to their relatives and roots on that side. If you feel you need to develop more spoken English proficiency, you might want to seek out opportunities to converse in English. Perhaps the idea of having designated 'English-speaking' times at home, such as at dinner, could work, however I'm not so sure that will work well if none of the adults are very comfortable with spoken English.
I understand your daughter is uncomfortable and confused at this moment. Sesame Street and other kids' programs, songs, and books on CD will help her. Just remember that her brain is a little sponge, and since she is in an English-speaking environment eight hours a day at schools and whenever she plays with friends, she will move through this phase of confusion really fast. I think the question is how to enable her to speak Chinese as she moves into her teen years. Lots of luck with it!