canine-
First of all, Pidyon Haben is not necessarily a simcha- just a technical aspect that has to get taken care of. (buying your son back from the kohen) Of course its a simcha once you’ve redeemed him…
To answer your question, I think theres a gemara that says something about being blessed if you have sons and cursed if you have daughters because if you have daughters you have to pay for the dowry and wedding.