I keep seeing all these smaller digital cameras with built in telephoto lens in the store. They are running from a $150 to a $400 price point, so I am assuming at the higher price end you are getting a decent camera- and it sure as heck looks a lot easier to haul around than the one I have.
So here's where I need to pick your brain- what am I losing by switching to one of these cameras for my trip? Any of these cameras you would reccomend? I just got the I phone 5 as well, so I suppose worst case I would have it to use...but I am assuming one of these smaller digital cameras has to be better than a cell phone camera, especially at the higher price points.
Don't necessarily assume a compact camera will be better than the iPhone camera - for most generic, outdoor, daytime snapshots, the high-end phone cameras can match a P&S camera - the only area where the P&S will clearly be better is when it comes to shooting things farther away, where the zoom lens becomes a big advantage.
As to what you are losing with the P&S superzoom cameras compared to a DSLR? A few things:
1. Focus won't be as fast, especially as light gets lower
2. Low light shooting capability - superzoom cameras have itty bitty sensors, usually 1/2.5", which are 12-15x smaller than your DSLR sensor, so they can't handle low light very well, getting extremely noisy and grainy, and worse, the noise reduction algorithms in the camera smear away all the details as the ISO goes up
3. Shallow depth of field control - if you like shooting with big apertures where you get that softer, blurred, out of focus background behind people in portraits and such, the tiny P&S camera sensors can't do that - the only option would be to use a lot of zoom and stand really far away
4. Lens interchangeability - that may not mean as much to you, but DSLRs advantage is that you can put on a different lens for specific needs, such as a fast prime lens for indoor shooting
There are plenty of other advantages of large sensors and DSLRs, but many of them likely won't really apply to your photography needs or your Disney shooting. Of course, Superzoom cameras have advantages too - namely a huge focal range in one compact, light body.
Other P&S cameras with larger sensors, like the RX100 mentioned by Havoc, will perform much better in more difficult situations like low light, but they don't have the kind of focal range you get with the superzooms - though it may be sufficient for something like a Disney trip...but if you were used to having a 300mm lens on your DSLR, you'll definitely be lacking in range a bit.
Mirrorless interchangeable lens cameras might be an option worth considering - the Olympus and Panasonic M4:3 cameras, or the Sony NEX cameras...they have larger sensors and can change lenses like a DSLR, but are much smaller and lighter, and pair with lighter and smaller lenses too. The M4:3 cameras use a sensor a little smaller than your camera, but bigger than almost all P&S cameras...the Sony NEX uses the exact same sensor size as your DSLR. This is a pricier option, but in the long run will give you a much more flexible platform that could effectively replace your DSLR while giving you many of the same advantages and cutting your weight and size of kit in half or more.
I shoot with both a Sony A580 DSLR, similar in size to your A100...and a Sony NEX-5N as a second body. To give you an idea of the size difference between a mirrorless body and a DSLR...I have a small waterproof camera bag I use when I want to travel light. In that bag, I can just squeeze my DSLR with my 18-250mm lens attached, if I reverse the lens hood on the end - I can barely close the zipper, and nothing else can get in there with it except maybe a spare battery. In that same bag, if I bring my NEX camera system instead, I can fit my NEX-5N body, the detachable electronic viewfinder, my 55-210mm lens, my 18-55mm kit lens, my Konica 40mm F1.8 fast lens, my 16mm pancake lens, my ECU1 wide angle adapter, two spare batteries, and my battery charger. And the bag zips closed comfortably!
That's a camera, 4 lenses, a lens adapter, extra batteries and a charger in the same space that barely squeezes my DSLR and one lens. And I still get a good focal range from ultrawide (18mm equivalent) to telephoto (315mm equivalent), with low light lens included (F1.8)...so I still have very good flexibility. All that fits in a camera bag that's about the size of a woman's larger clutch.
