How to get response with fields filled in by reply mail

dear all

i organise many events and the invitations are posted individually to many
persons. along with the main letter, i attach a sheet to be filled by the
invitees regarding participation, booking of travel tickets, accommodation
etc. they fill in the form and send it to me for consolidation. all these
are done manually, sending the letter and the form either by post or by
courier.

what i want to know is:

whether the invitation can be mailed individually (using mail merge)
in yahoomail.

can the above mentioned form be attached to the mail.

is it possible to receipients to send the filled in forms without any
covering letter. after filling in the details, somewhat "submit"button
to be shown, and when clicked it automatically sends the attachment
to me.

your help and advice are needed.

thanks

m s narayanan