The problem with SLRs are its size and carrying multiple lenses to take full advantage of the system. Nice thing about high-end P&S cameras these days are that they provide long optical zoom and lots of mega pixels (but on a small sensor so it is bit noiser but there are sw filters that do nice job to clean that up - noise ninja, neat image).
I am assuming the comment:
"I was looking for something with a great zoom, great lightning so that I can take beautiful pictures of the Vatican even few hundred yards away"
Means you want a good postcard images. And great lighting means good color, saturation and vibrance, and not flash.
I too have, no longer thank goodness, traveled significantly over the years and found that SLR to be too heavy and bulky for my taste. That said, I use DSLR almost exclusively now with pocket-sized thin P&S handy for non-critical shoots. The latter does not shoot raw and I don't care. It takes quite good jpeg images. For me an image is about capturing the moment and being there at the right place and the right time. I carry the P&S when I am not thinking about taking photos but just out an about or don't want camera to get in the way (e.g., skiing, biking, playing with my kids,...).
My recommendation is to first ask yourself what are you willing to carry/lug around on travel. If you want a DSLR, the recommendation of D50 with 20-200 zoom may be the best bet so that you don't have to change the lens but it sort of defeats the purpose of SLR (there is Cannon or other brand equivalent, I know about Nikon because I shoot Nikon). That said, already, its over 900.00, I believe.
Or, you can buy one of 10 mega pixel P&S with large zoom. You can crop further to gain additional magnification effect, as long as the optics are good. This, I know you can find for less than 900.00 complete. And your family can point and shoot as now.
Aperture will work with jpeg, or tiff but it works best with Raw files as long as Apple supports the raw format you shoot (D40 is not supported yet).
The second poster provided you with a link to G7. The site, Luminous Landscape, is an excellent site for understanding various aspect of photography and I highly recommend it.
Here is a link to DPReview that provides reviews of various camera.
http://www.dpreview.com/
Good luck.
MBP Mac OS X (10.4.8) Boot Camp/XP Pro