good stuff here. Forget the locks, those tiny locks are as good as no lock. If concerned, pack a couple zip ties (like they use for cables etc) and use those. You'll have to cut them, but they work great in a pinch. But thieves are crafty, they'll just cut your bag with a razor and catch what falls out if they want to. Just being aware of surroundings is usually enough.
Last time I flew to Germany a gate agent walked around, lifted people's carry on and marked some as heavy with a yellow paper tape thing. i don't know if they had to gate check those, as I avoided him by walking around, getting in line at the ticket counter and taking the escalator one level up. My bag way way over limit, at some 30+lb. Also had it on one of those collapsible luggage rollers.
TSA is no problem, sometimes they make me fire off a shot with the camera and ipad or laptop always has to go through in it's own box. But no dangers there. Once I had to pack stuff out of my carry on at check in, they wanted to weigh it. Now I hide the bag behind the counter or of somebody takes me to the airport I have them take my bag and wait elsewhere.
Also cargo pants and a jacket with big pockets can help, if in doubt just put some things from your bag into your pockets for the time being. You're not bringing all that much, I don't see that being a problem at all. I brought two bodies, two flashes, 4 or 5 lenses, chargers, batteries, etc. I also ended up using one body, two lenses so since then I rather err on the side "wish I had my 14mm for this one single shot" and live with the limitations. Usually no problem. Depends a bit on where you're going and what you want to shoot of course.
If you're going somewhere sketchy, maybe get insurance. Pick pockets (often pretty girls in Europe) look for easy targets. Don't be one. Wallet in front pocket, camera out of sight if not in use, etc. But don't get all paranoid either and let it ruin your vacation.
In Paris I had my camera on a sling and carried a simple shoulder bag on the same side. I put my camera underneath (out of easy sight) or inside the bag and sometimes had one extra lens in there, rolled into a tshirt. I also prefer the kind of bag that opens from the back so in crowds nobody can open it and get at my gear. If I sit in a caffee I put a leg of the chair through one of the shoulder straps of my bag on the floor, no grab and run that way. Phones are hot ticket items to steal, know where it is.
Oh, if you have one, bring a small p&s too. I got pretty tired of dragging my heavy camera around Paris on hot humid days and just took the small G12. And many museums and other places don't let you in with a backpack, you have to put it in a locker or leave it at the coat check. If there is one.
The lighter you can go, the more fun and less stress you'll have.
Have a great trip!