We have a really good lead on getting tickets to the opening match of this year's UEFA Euro 2016 tournament being held at Stade de France. I'd be going with my friend and her children. Even though Stade de France was one of the sites targeted, and this is a very high profile sporting event, we feel pretty secure knowing security is likely going to be a lot tighter than it normally is and it's an event that would be very cool for the kids to see as they are soccer fanatics. Being from Boston, we've had our own attack at a high profile sports event, so yes, stuff can happen anywhere. And it can happen at home just as easily as it can while you are traveling. It doesn't mean life has to come to a grinding halt out of fear over what might happen.
Frankly, it's just not a good thing to play "What ifs" scenarios because you can essentially do that all day long if you really felt like coming up with a huge list of all these bad things that could happen to you and your family (i.e., "What if the brakes stop working on the car while we are driving down a steep mountain?" "What if someone shoots us while we wait in line for the museum?" "What if ISIS plants explosive devices on the plane, or at a subway or train station?" "What if a giant asteroid comes hurtling out of the sky, hits the middle of the ocean and sets off a mega tsunami that wipes out heavily populated coastlines all across the entire world!").
I would suggest you not plan a trip to France at this point in time, and don't even tell your kids why. Just say it's not in the cards at present and leave it at that. Make plans instead to travel within the US to somewhere you do feel safe, or just don't go to France or any other European country you feel is too risky for you to handle without becoming anxious. Maybe Iceland, Ireland (not Northern), Luxembourg. You don't hear too much about terrorist attacks in any of these places.
I have multiple relatives who live all over Europe and somehow they take trains, ride subways, eat in restaurants, attend sports events and concerts, go to museums, shop, sit in parks, drink at bars, commute to the office, and they do these things every single day without being anxious the end is near. No one here (unless they work for the CIA) is going to be able to give you any guarantee that security is going to improve enough in the coming years to meet whatever expectations you might have about what's an acceptable level of "safe" for your family. It could be your kids wait until they grow up to see Paris on their own. And that's totally ok. Just don't taint their view of an entire country being "unsafe" based on these acts. I have known someone for nearly 25 years who always talks about how she admires that I can go overseas and travel. She also wanted to do those things at one point in her life and even went so far as to try to plan to travel with me several times a few decades ago, but every single time she backed out. Her mother was a very anxious and fearful person and she would hear of my friend's plans to travel overseas and would talk about how scary and unsafe it would be to travel through a foreign country. My friend has never left the United States. Her mother is now dead and gone, but that sense of anxiety and fear continues to live on in my friend. It would be a real shame if you share your fears with the kids and get them playing the "what if" game in their heads now to set them up for a lifetime of anxiety over things that have a relatively small chance of happening while they are traveling.