Yes you are right. Im still planning for my trip to disney but I dont want it be JUST for that. Hell of an investment just for that. I also want it to be a good camera for family outings like hiking. Waterfalls, micro on flowers, whatever. Also would use it for portraits during big holiday family gathering.
For places like Disney... honestly that's where I'd probably just use the camera in your phone (and I almost never use the camera in my phone -- so that's saying something). There are two reasons for this...
1) Usually when I shoot, the entire purpose of the outing IS to do photography. It's not like I'm doing something else and just happened to want to take photos. When you're going to Disney, you're definitely _not_ going because you heard it's a nice place to take photos... you want to enjoy the day. Also, you're not going to win any prizes from photos you take at Disney (and it doesn't matter which camera you use). It's not really the spot to try to get award-winning photos. You'll annoy your family/friends if they have to spend the day posing for shots. So this really is the sort of day when you just want to grab some candids of everyone having fun. You don't need specialty gear for that.
And since you don't need specialty gear... you also don't want gear that gets in the way. I'm not going to take my DSLR and collection of lenses on any rides. And since I'd probably like to enjoy the day... I want a camera that can fit in my pocket (or is at least a small lightweight camera.)
A Canon PowerShot "G" series camera (these are Canon's most advanced point & shoots... before you get into the DSLRs) is probably the biggest camera I'd be willing to take. But I think a phone with a decent camera would probably be what I'd use.
2) You mentioned some indoor venues such as theater, symphony, etc. This is a big red flag.
Generally if you have to buy a ticket to get into the event... then they likely have a photography policy. I used to shoot a lot of touring bands. These are the sorts of things where you would buy a ticket and the venues do have photography policies. But I was fairly connected in the music industry... got to know a few artists and labels... and they'd arrange for me to have a "photo pass" waiting so I could shoot the event.
HOWEVER... without that "photo pass", these venues all had photography rules. Generally the rule was no "professional" cameras allowed. What's a "professional" camera varies by venue. For some it was "no camera with a removable lens" (that means only camera phones or point & shoots with fixed non-detachable lenses.) For some it was "no lenses longer than 6 inches" (seems rather arbitrary but it's their rules).
This means it is rather unlikely that you'd be permitted to bring a camera with removable lenses to any Broadway show or symphony performance (without knowing some contacts who can get you a special pass.)
But overall... it sounds like you just want a general purpose camera that isn't necessarily optimized toward any one use. We could literally just suggest you buy the most expensive camera you can find if you're worried that every corner-case you might think of is covered... but honestly I think any decent modern camera is going to cover your needs.
But getting back to the question about shooting in poor lighting. Generally the lens wins.
When the lighting is poor... you might have to crank up the ISO to 3200 or 6400, etc. to get the shot. and when you do this, you start to lose dynamic range and increase "noise" in the image. A "full frame" camera generally buys you maybe a stop... two tops... of extra ISO before you notice the noise (as compared to a camera with an APS-C sensor.)
HOWEVER... a nice low-focal ratio lens will usually get more. A typical zoom lens is a variable focal ratio and usually something like f/3.5-5.6 meaning it's f/3.5 at it's wide-angle end and f/5.6 on it's telephoto lens (and usually not a linear distribution... usually by the time you're half-way through the zoom range it's already at f/5.6)
An f/4 lens collects literally double the light of an f/5.6 lens.
An f/2.8 lens collects literally double the light of an f/4 lens (or four times more light).
An f/2 lens collects literally double the light of the f/2.8 lens (four EIGHT TIMES more than an f/5.6 lens)
An f/1.4 lens collects literally double the light of the f/2 lens (or SIXTEEN TIMES more light than an f/5.6 lens)
So while the "full frame" body might get you one or two stops of better ISO before you start to notice the "noise"... the right lens can get you 3 or 4 stops. So generally the lens will do more.
This doesn't come without trade-offs. Shooting at very low focal ratios also means having a very shallow depth of field. I've taken concert shots at f/2 where unfortunately the microphone was in tack-sharp focus... and the face of the performer was a little blurred. That's not a keeper. So you really gotta be careful when shooting at these very low focal ratios.
