Inviting Co-workers - Need advice (Very long story, sorry!)

I am so lost as to what I should do as far as inviting people from my office. It's a long story.

I used to work in the accounting dept. and was very friendly with my co-workers and boss (the Controller). Some of them even got me really nice engagement gifts. We would talk about the wedding a lot and I had mentioned once that I would probably invite them. I was also somewhat close to the CFO. Therefore, I planned on inviting the CFO, my boss and the rest of my dept. to the wedding. Easy enough. No hurt feelings, no detriment to the future if my job. No questions asked.

It's amazing how much has changed in just a few months. The CFO was fired and a new one came onboard. Then, I got promoted to become the HR Manager. There was never anyone doing HR all the time in the company (I did it as part of my accounting job since I was going to school for it). Now, I am the entire dept. Me, myself and I. I report to the new CFO, who I am not too fond of.

I also in the meantime became very friendly with the Exec Asst that the new CFO hired in.

My concerns are this. Who do I invite now? The accounting dept has changed since I left due to a new hire and some restructuring. Some of the girls there don't act the same towards me and honestly, it's nice to be away from them sometimes. I am still somewhat close to the controller (but not like I used to be obviously).

I was told when I started my new position that I am now a 'manager' and need to allow myself to step into the 'higher' level. So now I am afraid of inviting people 'below' me (I hate thinking of it in those terms) in that it may cause issues in my position and with the management of the company (we are a somewhat small company). I don't want people to think I am favoring certain people.

I thought about not inviting anyone at all. Is that wrong? Shouldn't I at least invite my boss? I don't feel comfortable just inviting him either. I don't feel close to him like that. Also, I really want to invite the Exec Asst since she has given me a lot of advice and we have gotten really friendly. But then how do I invite her and not the others? Argh. This is so hard. I hate this part of it. Anyone have any advice? Thanks.