Since you're already into the F-Stoppers Bags, have you not considered a smaller one of those? I have the Guru and love it as a day bag. I think you'd be able to fit all that stuff into a small ICU in the guru, though the lens hoods might be a bit of an issue and the 70-200 would have to be attached to the camera. I also have the Medium Slope for mine which would easilly fit that stuff, but leave less room up top for jackets etc.
I agree, since you've invested in the ICU why not try the Guru or the Kenti? F-stop makes really great bags. Perhaps the best camera bag out there.
I use the Tilopa BC with a medium pro ICU for mulit-day backpacking or trekking. I used to used a Guru with a small ICU for daily walk use around town. Now I have a Kenti I don't use the Guru anymore.
The Kenti cannot use the ICU system but the bag is awesome. I use it for day hikes. I take a 5DIII with 16-35L, a 7D with 70-300L with hood and tripod ring or 70-200L without the hood but with tripod ring attached, a 24-70LII, one 600ex RT plus radio trigger, Lee filter kit and holder, extra batteries and charger, intervalometer, light meter, iPad mini in a Logitech keyboard case, rain coat, gloves, head lamp, flashlight, Leatherman tool kit, some snacks. I can carry all that but not look like I carry all of that. The Kenti is designed very well, you can even add some extra holder on the hipbelt (I added a water bottle holder). You load the camera with lens attached from the sides so you have easy access to your gear at a moments notice. The top compartment is roll top so it can expand to carry as much gear or enough clothing for a weekender. You can also attached a camelback water bladder on the outside using one gatekeeper. and you never had to worry about the leaking inside the bag.
Trust me, you will look cool with a Kenti. Your grandson may even want it from you.