Think about the population you want to serve as an FNP and why you chose the FNP track over, say, adult health, mental health, or gerontology. I'm going to hazard a guess here that you were drawn to the FNP track because of an interest in families in all stages of the lifespan but that you have a particular interest in the childbearing and childrearing years.
Do a little bit of soul-searching and reflecting if a research question doesn't come to you. What things have you experienced in your career so far that make you think they could have been handled differently? I see that you have ER experience. You've probably seen families come in and be totally stressed out over worries about a child who is injured or ill. What are the sources of their stress? How could their stress be alleviated? What do you think you, as an FNP, could do to help alleviate their stress? Could some sort of complementary therapy such as armomatherapy or music be helpful?
If you still aren't finding anything, you might want to just peruse some of the current literature so see if anything in particular interests you. Look at the latest issues of some of the peer-reviewed journals specific for advanced practice nursing. What are some of the trends in research? Where is nursing knowledge headed in your particular area of interest? Do any of the topics appeal to you more than others? I know a student who was so excited by what she read in one article that it inspired her to look for more research on that topic and the articles she found are becoming the foundation for her project.
It also helps to brainstorm with your peers, just as you are doing! I hope you are able to find something that suits your interests but do keep in mind that if you find something for your lit review but it doesn't really float your boat, it is okay to change your mind along the way. You may also find that your original clinical question changes over time---that it narrows or broadens or takes a different form than you had anticipated. For example, you might decide you want to look at the effects of calming music on unruly kids and stressed out moms in the ER but you end up deciding that you want to look at how the stress of the ER environment can be a barrier for patient and parent teaching. And that's okay! Yeah, it saves a lot of time when you already have a topic in mind and don't deviate from that, but realizing that you can change your mind should take off some of the pressure to find the "perfect" topic.
Hope this helps!