I think it is perfectly fine to have a shower in your situation.
Personally, I think babies of different genders or when they are pretty far apart in age should still get showers
During all of these women's first pregnancies did you all not have showers for gifts that people brought to you in honor of your baby? Whether or not its your first or second pregnancy you are having a shower for the same reason each time...GETTING GIFTS FOR YOUR BABY! If you look at it as being grabby then you should consider yourself grabby for having a shower the first time. You are the parent and are responsible for both your first and second child. If its not ok for people to buy you things for your second baby then it should not be ok for them to do the same with your first child.
I am in the same position. I am only 5wks 6days and my best friend is wanting to do the same. I have a whole new group of friends now, I am with another man due to uncontrollable circumstances on my part, and my son is 9. I didn't plan on anymore children so there was no need to keep his baby things. I have not agreed nor disagreed bc I am still very early in my pregnancy. If your friends are offering you a shower and you are comfortable with it then go ahead.