We always go to Kiddie Kandid they will do pretty much whatever you want - group, kids, family, individual all in the same sitting. You can do a package or buy individual sheets. Packages are usually better deals and you get to pick the sizes and number of pictures of each pose. Average cost would be about $80 to $120 and there is no sitting fee. They take their time, work very well with kids and if your not happy, you can always come back and have the session redone (say maybe your son was just NOT happy that day). I've always been very happy with them for inexpensive photos. And you get your portraits as soon as your finished picking what you want! Holiday Cards are also available and maybe part of a package right now (but maybe not until closer to the holidays).
I've tried Sears, JC Penny's, Target photo studios and have not been happy with what you get for about the same price. And I can recommend a very high end photographer if you're interested, but his prices are in the hundreds (but you get what you pay for). I've also been to Fotogenix by South Towne Mall, they did a very good job, but with a $60 sitting fee and only one 11x14 we spent $80 on, I didn't feel we got a lot of bang for our buck.
Have fun getting pictures taken. I suggest going in the morning or after a nap when kids are usually pretty happy and cooperative. And bring a snack for after!