I have both...long story, but if I could only have one, it would be a tough choice. If I had LightRoom (which I don't), It would make the choice easier..I'd use it with Elements 8...ESPECIALLY if I were using it in the way you described you'd use it.
CS5 has some features that Elements doesn't, (rumor is it does, just disabled)...and it's really about what you need...Plus Elements has two other "quick" editing modes that walk you through so it makes 99% of what you'd do that much easier. And most importantly ..faster!
I've had the older (pre-"CS" versions of Photoshop)..The the first version of CS (no number), CS2, and then gave up on it and didn't really have an interest in it since I didn't have a need for it...I used film until a year ago for stuff I cared about...and did more with Photoshop that had nothing to do with photography than it did with graphic design..after all, really it's a graphics program, and in fact I know just one person who uses Photoshop all day every day and I don't think she uses it for photo manipulation more than a few times a year..She designs logos and stuff like that...no photography involved...For her it's more like painting without the mess and clean-up.
Just last April (a year ago) I got my first dSLR, and realized I'd need to bone up on post processing...So I bought Elements after downloading the trial versions of both PSE8 and CS5...couldn't justify the expense of CS5...But I ended up with a free version so now I'm struggling to learn it, and while I enjoy the challenge, I can tell that even having used PS for a decade, the learning curve is steep. While they did make the interface a bit more "user friendly", they also made the program so much more complex that it's not any easier to use (they actually combined two programs into one..PhotoShop and ImageReady..so it has to be bigger and more intricate.
Recently I couldn't find my favorite picture of my wife...just a tiny little color print. Fortunately I had sent her brother a copy when I got the prints back from being developed years ago, and he still had it..it was in rough shape, but he took it to Walgreens or some place like that....had a copy made and mailed it to me. I tried my best to restore it using both CS5 and Elements and couldn't get it right. I took it to the guy in town who works at a high end camera shop and rarely comes out from the back where he does post processing for the people who rather pay to have it done (very affluent area).
He got the picture to look better than ever...I was hoping he could take this tiny print and make it look decent at 5x7 or so...it looked so good at 5x7, I had him send the file to the lab and blew it up to 11x14...which I have now and want to get an even bigger enlargement... (I was widowed at a ridiculously early age, so it means a lot to me)...I'll probably keep blowing it up until it's nothing but grain.
He did ALL the restoration using LightRoom.
The 30 day free trials will give you a better idea than anyone here can give you, so I'll just give you this link for some entertainment...It's just over one minute long condensed probably of hours of work getting ready to shoot a headshot of a model....there's just a few seconds (don't blink) of Photoshop being used at the end....although what's done can be certainly be done with Elements...and the truth is I'm only guessing it's Photoshop, and not Elements..could truly be either. Very entertaining.... Enjoy!