Assistant manager position

Hi everyone, I need some real advice please. I’m in a tight position and I don’t know what to do.

I work for Nordstrom’s and I’ve been a sales person for almost 2 years now. I am commission based only and you could earn really good money when it’s busy, otherwise your checks are crap. This is one of the reasons I wanted to grow aside from the fact that I really enjoy working here. My position right now is very easy going and flexible which is a plus for me as I have kids. My 2 year old will be starting pre school soon and my 10 year old stepdaughter has a cheer during the week and competition often which I’ve missed due to being at work. I know once I become a manager this will get harder. I will no longer be able to do the things I can do now. Majority of the time the kids are with my husband and I don’t have time since I’m always at work, becoming a manager will be harder and I know that sometimes we have to sacrifice. But so far I’ve heard nothing but negative things about the department manager who I will work with 98% of my time.

So to start off, she lies about why she isn’t coming to work sometimes. For example, she took two weeks off to go on a yacht vacation on the beach while she told her employees she was going to a funeral. She told me she takes sundays off to go to church, my manager says it’s a lie and she likes going to brunch. It seems like she has a really good schedule and I won’t. I will be closing a lot while she will be opening and off on Sunday’s. I will have to be at work every weekend and two days out of the weekend. She leaves early from work all the time and she’s hard to find when she’s there. The assistant takes care of everything which shouldn’t be that way. Department managers are always in their department but this specific manager is all over the place and hardly comes to work.

They say she’s lazy and doenst teach things right. Her last assistant hated her because she would not do anything and wanted the assistant to take care of everything. Which is why she left.

I’m just really concerned about my family and not being able to see them at all or hardly ever. So I just need advice. And if I shouldn’t take the job, how I tell my manager who has had my back since day one and is pushing me for this assistant position. Now the store manager is also included and she loves me which is why my manager wants me to go for it.