Step-Mother of the Bride questions… Looking for insight?

My Step-daughter is getting married this summer. We are close in age; her husband to be is less than two years younger than I am.

It’s an evening wedding and it’s semi-formal (not black tie)
The ‘theme’ colors are clover green and yellow

Her mother is wearing…something kind of dowdy, not very “summery” and it doesn’t coordinate at all with the theme colors (wedding party colors)

A very good friend of mine said “your job is to not outshine the mother of the bride, next to your step-daughter and her husband, this is her big day too”

My sister says that I should only be concerned about what I wear being complimentary to my husband and tasteful, that my “job” is just to look good and make my husband look good.

My husband says “wear something that looks good” (because he’s such a help!)

I’m not really in tuned to wedding etiquette so I don’t know what to wear and would love some suggestions

Also, now there is the planning of the shower…

The maid of honor and I are friends and she contacted me about places to have the bridal shower, ideas, etc…

Her Mother is out of work and has no car, so she’s not financially able to contribute, but I don’t think she should be totally left out of the planning process

I’ve offered to help pay, how much more involved SHOULD I be in the planning process?

(and if anyone here has any more experience in this realm, what other problems should I look out for in the future?)