Some guidance needed for application of a visitor visa.

[earthlling]

Hi, i am planning on calling my brother and his family(wife and 2 children) to the UK to attend my sisters wedding.
I have never done this before so bit confused as to where to start. I've been reading info on UKBA wesite. But i still have few questions so was wondering if someone in the know on here could help me.

UKBA site allows online application, can i fill that form on my brothers behalf from UK?
How do i send the sponsor letter and other documents from here, as in do they have to go through a solicitor?
Is the £3000 bond thing starting in November, if so if i fill the application form in the next few days i should be ok shouldn't i?
About my finance, i have a few accounts, but my main account(where my wages go) is always in overdraft(i have £1500 interest free overdraft) but i have close to 14k in my other accounts. Will that be an issue?
My brother has been to the UK twice before once on his own and once with his family.
I have a 3 bed house which i own, also have a business and i work full time.

If anyone would kind enough to answer the above questions, i would be very grateful.

Thanks in advance.