I reckon those lenses will do fine.
Your biggest challenge is going to be swapping lenses; if it is dusty then it is a mare and if it is muddy then you can't put anything down.
For an illustration of mud have a
look at this; drop anything while changing lenses/batteries/cards and it is likely to either vanish into the depths or be a write-off.
I use two bodies and try to avoid changing lenses unless I have to.
You should consider using both bodies. Perhaps the 40D on the 24-105 and the 7D on the long lens ?
Also worth thinking about your bag.
A messenger style bag or a wide rucksack is very difficult to get through crowds.
I've got a slimline backback (no side pockets) with an all weather cover and access from the back (Lowepro flipside sport); means if I need to then I can lay it in the mud and get proper access to the bag and none of my straps or kit get muddy; when the bag isn't over-stuffed I can also get to all my gear without putting it down, but that doesn't usually work that well for me
It is worth packing a head-torch to use while sorting your kit out as the corners where people aren't standing usually have no light.
I also carry a bottle of water, some wet wipes and an extra layer in case I get cold. Plus I have occasionally caught my self shaking with fatigue; so carrying a Mars Bars for instant energy is sensible.
Have fun