Registration requirements vary somewhat in the 38 states and the District of Columbia that require registration prior to soliciting charitable contributions within their states, so ultimately you will have to consider the statutes of each state where you intend to have solicitation done on your behalf.  Assuming, however, that you are not paying the trade association to solicit for you (in which case rules on professional solicitors or fundraising counsel would come into play) in general you will have to be registered in each of the states with such statutes in which solicitation will be done.  In addition, the trade association actually doing the solicitation will have to be registered, even though it is not a charitable organization, because it is making the solicitation on your behalf.  There are some states (although not all) that exempt organizations that solicit only bona fide members, but those statutes normally contemplate an organization soliciting its own members for its own programs.  They do not contemplate an organization soliciting its members for another organization’s programs.