kitzur_dot_net: you are correct about rabban gamliel, except two things. one he was a nassi, and had the power to issue takanos. and two, in that takana he was issuing, it was for kavod hames, something that is considered more importatnt then kavod hachayim. it was not made for teh serviving family, but for the actual person being eulogized.
also, if he is to be your source for issuing takkonos, are you aware that the wealthy of his day made weddiong that lasted days. and the poor just had a minyan. so i will take your proof and say that it is clear from rabban gamliel that one may NOT issue takanos for chasunas.