How to include goddaughters

So we are getting married in April and planned to have our 18 month daughter flower girl and 3 year old son ring bearer. My FH best friend passed away recently and FH wants to include his 2 twin girls in our wedding somehow. They are almost 5 years old and my FH is their godfather so this is extremely important to him. I agree with having them involved just not sure how. I really don't want 2 more flower girls though. I found a dress for them that matches my daughters exactly except it's pink tulle skirt instead of white like my daughters. All the bridesmaids are wearing pink. I thought maybe they could hold ribbon wands and shake that around. I thought about blowing bubbles but not sure about if that would stain clothes and how that would go. Any other ideas???