Flower girls

My DD"s will be the flower girls in my SIL's wedding next Sunday.  They are 19 months and 3 years 4 months.  Both are really excited.  I had all 8 of my nieces and nephews in my wedding and they did great.  I was the bride with the whatever happens, happens mindset and DH and I really just wanted all the kids to be part of our big day.  My SIL has been totally relaxed about all of this until this week.  She is also having her FI's nephews in the wedding who - the youngest is the same age as my oldest.  The director of the temple got her all nervous and upset by telling her she should not be having all these little kids in the wedding and how if they cry, they will ruin it and other crap like that (so not her place to say these things but that's beside the point).  I have reassured my SIL that the baby sitter that we hired to be there that day will take the girls out if they are crying or making noise and if they don't walk down the aisle - she will keep them happy.  SIL is fine if they walk with DH and I who are also in the wedding or with the little boys.  We bought the girls little beanie baby brides that my mom will have as a surprise for them after they walk down the aisle (we will tell them that Grandma has a surprise waiting for them when they get to her).  Any other tips or tricks you can share for things you have done with your DD's or with the flower girls at your wedding?  I'm just trying to keep my SIL from worrying about how the girls will be as she has way to many other things to busy with right now.  Oh - my sister and BIL will sit about halfway down so they can help if needed too.