Hmmm, well I am sort of having the same issue as far as deciding to send invites/std's to EVERYONE. I have decided to not send invites to people who I for sure know won't go to our DW in Mexico (for example...second cousins who live in another state that I talk to maybe once a year, or my moms friends at her work) For those people I will send them an AHR invite later on but those are going to be very simple.
I don't think you necessarily have to send both the std's and invites...your website will probably have most information anyway....and if you are on a tighter budget by not sending std's you will save some money. Money maybe you can use towards your invites? just a thought!