How to say this delicately...You don't just send people information on your registry if you are not inviting them to the shower. And even then, some purists think it is still a serious violation of etiquette to send registry information with a shower invite. The reason is that it suggests that gifts are required when they are always optional.
While I am sure your intention is to make things convenient for those who *want* to send a gift, the more polite way to do that may be to wait until someone asks you (or your mom, sisters, aunts) about it and then you can start to spread the word.
I am also pregnant with my first and while my husband's family is all close by and will attend the shower, my friends/family are all spread out. So I understand wanting to get the info out to in a fast/convenient way. But I still believe you don't want to give people gift information unless and until you are asked.
Congrats on your baby and good luck.