My girls are much younger at 5 & 7 but I personally felt it was very important for us to include them in our scans...This is my OH'S first baby but he treats my girls as his own always and he fortunately for me agreed. I don't want the girls to feel this baby is any more important to either of us and the scans were a way of showing them this.
The girls came with us at 12 weeks and 20 weeks and loved it (my eldest sulked tho because I didn't want to find out what sex we had haha)...but it was a great experience for all of us.
On the flip side both myself and my partner wanted to have our private 4D scan on our own so we booked it for a time when we didnt have the girls with us. It was lovely to be able to concentrate on our growing baby rather than them distracting us too ! We shared the dvd and photos with them after of course. Maybe this is something you could do with your daughter so that she doesn't feel left out and could be a good compromise if your OH really is against it...she may enjoy the 4D experience more. Each family is different I guess I hope you can reach a good conclusion for you all and it doesn't overshadow what should be an exciting time for you all.