I wouldn't get rid of the 40D mate. Mastering exposure/lighting will make a 300D deck your 40D for photographs in ideal hands.
The 5D would produce better skin tones but within your style I wouldn't say this is a massive issue.
The technicals of both cameras would sway more towards your 40D. You'll loose the fun of live view and the handiness of onboard flash.
The Frames Per Second of the 40D are gonna come in super handy when you do your wedding in the fall. You'll wanna be firing off a couple of shots as quick as possible to bypass those eyes that are gonna be closed in a few of your pictures (being your first wedding it may happen more than you'll think)
Glass always outweighs a body. You'll be making 2mp over your 40D whereas the clarity of an image/better quality will come from the performance of the optical lens.
5D mark II for its sheer excellence, Yes
5D you simply wont see the difference.
You're the photographer regardless of what kit you have. 40D, 17 - 40L, 24 - 70 2.8 L. 50, F1.4
Hello weddings and portraits. Invest in the 24 - 70. Look at upgrading your 50mm one day or even the 85 1.8 (might be too much tele zoom on a 1.6x though so stay with the 50)
You can kiss your 55 - 200 off on a FF camera. It wont even be a joke.
Hope this helps