For backpacks, I really like the Lowepro Flipsides. I've had a Flipside 400 for a few years and love it. Lowepro makes some quality stuff. For hitting the parks though, I prefer a smaller messenger bag and a lighter kit vs backpacks. If had your gear, I'd take off the grip and pack the 7D, 18-55, 10-22 and get the smallest Crumpler that fits it all. 430EX as well if you're going with kids and will be doing character shots / dining. For the most part, camera will be on your neck and spare lens in the bag so a backpack would be overkill imo. Only time I put my camera away is when boarding a ride. We have a trip to Disney World coming up soon and my kit this year will be the 7D, 17-55, 11-16, 430EX, and Lenspen in a Tamrac Rally 6. Didn't take the 11-16 last year and fit it all in an old shoulder kit bag from my 35mm days. Worked perfectly. Found myself wanting to go a little wider at times though. I've never been to the left coast parks so can't speak to attractions which would warrant a telephoto. Good thing about the 55-250 though is you can probably fit it into whatever bag/pack you choose along with the other gear.