Q. Should a seudas hodoa or a festive meal be done for the newly converted?
A. Madrich Lager (p. 86) quotes that some would advise not to do so, since this seuda is not mentioned by the Poskim. However his opinion is that in principle a thanksgiving meal should be done as we do in a bar mitzva, and it would be considered a seudas mitzva.
Horav Moishe M. Lowy Shlit’a mentioned that we find that Yisro made a Seudah after he was megayer. (Ramban). Therefore, it would be appropriate to make some type of Seudah.
Horav Shlomo Miller’s Shlit’a opinion is that it is best to serve a kiddush or similar as a seudas hodoa.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a