Anne, I love the dress you plan to wear for the wedding--and it will photograph very well. The only thing to be cautious about, is standing next to someone else who is wearing a print. You may want to make sure your children and husband are in solid colors, since they will most likely be near you in the photo. You may also want to check in with other members of the family and see what they are wearing. I know it sounds like a lot of work, but picture a group of people all wearing Hawaiian shirts, and you'll get some idea of what could happen if more than 3 people wear bold prints.
BTW, when I was fresh out of college, I worked as a photographer in a portrait studio. By no means was I a "school trained photographer". The company had their own training method and special cameras that made photographry fool proof...but I did learn a few things about clothing and groups and backgrounds.
Which reminds me...will this photo be outdoors? If so, and if everyone is dressed up then it might be better to move the photo indoors. I remember we had these outdoor back drops that I hated to use--but when customers requested them, I had to use them. I was supposed to use them a certain percentage of time, and woudl get in trouble for not using them--but they were really tacky and fake looking. Anyway, there was a winter scene and parents would bring their kids in for a photo, in little dresses and suits and then want a photo taken in the snow scene. I was like---uhh...who stands out in the snow in a dress and suit?? But some people just had to have the snow scene regardless of what their kids wore.
So, there is lots to think about regarding what to wear for this photo. But overall, I think your outfit will work if 1. there are not a lot of other bold prints in other people's clothing (esp people who are standing next to you.) 2. the photo is taken indoors instead of outdoors. 3. everyone in the group is dressed at the same level. (If everyone else is wearing khakis and jeans and you're wearing that beautiful dress, you will look out of place.)
And most importantly--SMILE!