Each family has its own way of doing things. It's not a problem if you want to let his and your family reach a final number, however, it is really for the groom (and you) to decide how much he can afford to give you. Others should stay out of it. In most cases, fights/issues take place when elders start to talk about this amount as the girl's side wants it as high as possible but the boy's side wants to set it as low as possible. Of course there are exceptions but I am speaking in general. But if your and his family won't argue over it, then it's best that the elders decide on it.
it would have been better than anything else if only both of us could decide the amount. In my situation its totally an aranged marraige and we both are not communicating with each other (no arguments on that). I have to leave it on my family since I cant discuss it with him. and my family is really concerned about making no issues on haq meher. they are ok with any amount. :)