There is an FAQ that basically says that "Of course you will need to declarte a path if interceptions are possible etc. (sorry we should have said)" or words to that effect. Take a look there on the site.
I have had the above sort of thing several times in games. FWIW this is how we played it out - so this is not an official ruling as such (wait for one of those):
1. You declare both charges and with them a path if there is a hint of an intercept or an evade. We always declare who a BG is charging however.
2. In the above there is no interception or evade so no need for a path at that stage.
3. The charges targets do matter and the Ellies are at both the Spear and the Knights at declaration as they are too wide to just charge the Knights. Had Hammy been in column he could have declared a charge just on the Knights by the Ellies.
3. You move all charges in the same sub-phase on the detailed sequence (see the table) but the charger chooses the order if it matters and here it does IMO.
4. If James does the Ellies first, then they contact as shown and it looks like the Cv may drop back one to get past friends hitting the right hand file, and expand to overlap on the right later.
5. If the Cav are moved first the cav go in and block the front of the spears The Ellies then contract by one as aloowed BUT they have to try to charge the Sp and the knight, their target hasn't changed. We played it that they contacted the Sp on the side edge as a frontal charge in column. Hammy then chooses which ones fight (having more bases) so probably chooses 2 dice from the Ellies and 2 from the cav and in Movement the Ellies conform to be an overlap. The Knights do not get hit in this version.
The wheel issues is interesting and not one I had considered but the intent of that is that you cannot wheel to get less bases in than you could by not wheeling. The fall back is not part of a wheel so I would say in this case the Ellies can wheel once in column as long as they don't get less that 1 base into contact

It's a separate concept to me. That does not however mean they can change thier target and the Spears get hit first and there ain't no 2nd base now to press forward.
Course that's not to say it is how it should work...
Si