I'm an atheist and attend AlAnon every week, sometimes several times a week. I have not yet identified my higher power and have struggled with the concept, although from shares at my meeting even those with a religious higher power sometimes find it difficult to place their trust outside themselves.
Despite not having a good idea of a higher power I have found myself being able to let 'hand things over' as they say and trust that whatever happens things will be ok. For me that has come from an increased trust in my ability to cope with challenging situations. I like to consider my higher power as the laws of nature, how things will carry on in their never ending cycle regardless of what I do. I look out to the stars and realise how insignificant some of the things I worry over truly are and am filled with wonder for the world around me. But I still struggle to pair that with some of the literature that focussed on a personal higher power, as I don't feel the laws of nature are in any way personal. But that's ok, I don't have to understand everything right away and I am free to take what I like and leave the rest. AlAnon has been so beneficial for me, outside of all the higher power stuff, that having something I'm not totally on board with has not beena problem.