Ways To Authenticate a (Real vs. Esignature) Signature

I would like to be able to send a client our contract and allow them to read and sign.  They will then fax document back to me. I will sign and date.  I could then fax the document back to them or if they do not have access to a fax then I could scan document and send back to them as an attachment to an e-mail, right?  But I am wondering about authenticating my date and signature.  What if I do not send the document back right away for whatever reason.  Then I realize I need to get the document back to client maybe the next day or even one or two weeks later (If I really goofed).  I need something in place to say or authenticate that I indeed did sign the document and to also 'guarantee' that I did so on the date that I said I did.  I think I'm making this too difficult.  Does anyone understand what I'm asking?  Yes I know I sound technologically challenged.  At least I am trying.  Right now e signatures and/or digital signatures are not accepted by everyone I work with and I am not aware of how I am supposed to go about authenticating my date and signature.

Message was edited by: teri schuddeboom