Why are you shooting the festivities? By that I mean, is it for publication, memories( I remember nothing after a 4 hours into it, except a crazy girl from Texas....but that is another story), or for art purposes alone.
Shooting outdoors negates any low light advantage for the d700 and in fact the base ISO noise is lower for the D7000. So it probably comes down to any expectations by a client or your own comfort. If shooting was the purpose, instead of participating, I would take both with a 14-24 or 24-70 on the D700 and 70-200 on the D7000. With the right carrier such as the double sling strap from Black Rapid would sure ease the concerns of weight. I shoot events all the time that are 8 or nore hours and carry a D800 with SB900, grip and 70-200 or 24-70 mounted and if I take the D7000, it gets the 70-200, a second SB900 and grip and the 24-70 or 85 1.4 and a flash and grip mounted on the D800. No other bag is needed, extra batteries, cards and cell phone placed in the pockets of the Black Rapid straps. If you do not use such weigh reducing straps, I would go with the D700 and two lenses that would cover wide and longer. Image quality will not be visibly different except possibly to a photo-editor. A bag is not good for crowds since there is no security, you can be picked without you even knowing it. If you can't keep the camera in contact with you at all times, attached to you, don't take any camera except a point and shoot or cell phone. It is a meca for sneak thieves who travel to large events where there are a lot of visitors who tend to be less aware of their surroundings. Stan St Petersburg Russia