I'm having this problem. My Y5 DD is due to go to London next month. She is ridiculously excited.
Already I've her dad, her gran and my gran on the phone telling me she is no longer allowed to go.
In all honesty I expect it will be cancelled/postponed but if it's not I'm leaning towards letting her go. The chances of a terror attack occurring during the three days she is there are slim, the chances of it happening close to her in a city the size of London even slimmer and that she'd be actually injured or killed should the unthinkable happen slimmer still.
I refuse to live my life in fear. If I did that how far do I let that fear rule my life? Do I avoid any and all major cities? What about events? Buses, trains, airplanes?
But then what if she gets run off the pavement by a drunk driver? Or targeted by a predator?
Yes the risk is higher in London, but then so is the risk of being hit by a bus or tram.
We travel to Manchester often, I used to live there so when my older DD asks to go to concerts if there's not a Newcastle date Manchester just makes more sense to me than Leeds or other closer cities because I don't know Leeds, I do know Manchester. This isn't going to stop me but it would make me more vigilant.