When to send baby shower invitations?

I want to have everything by 36 weeks so we were thinking on an April 28th get together. I just want to know how far in advance I should send the invitation and registry details. Is a month enough or should I send them this month. Guests coming that are furthest from us are 4hrs away. Everyone else is too far and won’t attend but some have already mentioned sending a gift through mail. Any suggestions?

I imagine my shower something like this while the post man might be very tired of walking to my apartment hahaha