i'm going to assume you're talking about an interchangeable lens slr
(where you can change different lenses)
i shoot on a canon eos 5D mark ii, so this may be somewhat biased, but like
the above poster said, the canon EOS Rebel T3 is a great entry level SLR.
the entry level canons do feel plasticky (and are lighter) compared to the
nikon entry levels. nikons have a much nicer feel and a sturdier body.
however, the best advice i can give you is: don't rush. take your time,
because it's such an expensive hobbyy. (i started off using nikons and
bought a few lenses, before i converted over to canons--the buttons
and knobs made more sense even though i like the 'feel' of holding
a nikon better) go to the actual store, and hold it, see if it fits in
your hands, see if it's light enough for you to carry around.
techs specs and all that stuff:
the biggest misconception about buying digital cameras is
higher megapixel = better images. not true! so don't use that as a
deciding factor. (entry level dslrs are around 12mp and you could
push out a 24"x36" foto from that, but the printing cost alone is like
$100 per print... so... megapixels is not where it's at)
things you should pay attention to is the
sensor size:
because
larger sensors + better lenses = better shots.
not to get too technical, the sensor size basically means:
the smaller the sensor the smaller area of the subject/scene
you'll capture, the larger the sensor, the larger the area
you can capture (see picture). to put in perspective, the largest
and most expensive cameras are full frame.
it's called the 'crop factor' read more here:
http://en.wikipedia.org/wiki/Crop_factor
kits vs body only: if you are starting from scratch,
it seems to make sense to just get a kit (a kit means you
get the camera body and a standard issued lens) and build your lens
collection later. but since you said you wanted to shoot kids...
the downside of kit lenses are that they're kinda slow so that
means you might have a harder time to get nice sharp and
crisp images of moving objects (like kids) and you'll usually
need a flash in lowlight or else it'll look like you're taking
pictures during an earthquake: shaky mcshake. and if you do
a lot of indoor shooting, a faster lens might help (because
it lets in more light: bigger aperture). a faster lens allows
you to have a faster shutter speed.
but also you will be taking a class that will probably teach you
how to take a variety of subjects, and a kit lenses is versatile
enough for an intro class. the cool thing about these dslrs is that
they also come with preset shooting modes, so if all else fails,
switch to that mode until you figure out all the knobs and buttons.
(i know all this might be confusing, basically when you're starting out,
it's hard to answer, exactly what it is that you want to be doing, so
going for something more versatile helps, until you know which
direction you want to go.)
the biggest pain in the ass when starting out with dslrs i think is
ending up with blurry photos because your hands are shaky. and
even if you think you have super steady hands, it's easy to end
up with blurblurblur. the technology on entry level dslrs have stuff
like image stabilization/optical stabilzation (anti shake).
also since you're shooting kids, go to the store and play around
with the continuous shooting mode, it basically lets you hold down
on the shutter and it'll .. well, continuously shoot. (that's my favourite
sound when playing with cameras).
also play around with the menus, even if you don't know too
much about the camera yet, see which one seems intuitive
to you. sometimes the menus on some brands get so many
levels deep and it's just ridiculous, you end clicking menus
more than clicking pictures.