You have options!
One, see who actually comes- then decide.
Otherwise, lots of DW brides have their guests in a color scheme of some sort... white weddings, wearing neutrals like white and kahki, etc.
I chose blue bc I feel like most blues compliment eachother, no matter what shade. I had all of my friends that would have been in my wedding had I chosen a more traditional route wear a blue dress of their choice and just had my sisters/SIL in the actual wedding party. You can still get ready, take pictures with all of your girls.
If your wedding is only going to be about 20 guests... have all of your girls sit down and you and your man stand alone.
You can still honor them with a gift like a cute bracelet or whatever but you will save a TON of money, your girls will be able to wear a dress of their choice, and you don't have to "take it back so to speak.