Telling Boss

So I'm almost 10 weeks and am terrified to tell my boss I'm expecting. She is not going to be excited, it is just her and I in our office, so she is going to have to pick up a lot of extra slack while I am out. She is also just not a warm person, and honestly has always kind of scared me, her personality is very off putting. So, my mom told me it would be appropriate to get a nice card and flowering plant and leave it on her desk the day I leave for vacation next week telling her the news and that we will discuss when I get back. I will note that I know it will be hard for our workplace and wanted her to have time to process and we will come up with a game plan when I get back. I know it's a cop out but I feel like I will chicken out and not tell her for weeks otherwise. Do you think this is a totally terrible idea? Any thoughts appreciated. Obviously, I know it would be better to tell her in person, but do you think this is a valid second option?