Well technically if you make these certificates, then you're establishing paperwork or a Provinance for those coins that you do sell. It might be useful to get a good digital scale (I have an Ohaus with an airshield) and record the photos as you've done and also the weight (in grams) of each coin. Don't make a huge certificate but maybe something 5x7" so the buyer can file it away easily with any coins they get from you. You might state "bought in bulk lot" from Israel or where ever you got them from but this hardly establishes authenticity. I know in "Treasure coins" e.g. cob silver & gold coins salvaged from shipwrecks, that various sellers have their own "certificates" printed up (not on a laser printer) which accompany the coin. I think Mel Fisher is an example. Maybe leave off the spurious sounding "Ancient Coin Ministry" and just have your real name and name of your church?
I do like tracing the provenance of my coins, as much as possible. I'm just getting started in ancients, so I don't have much data yet. As far as I understand it, the Israeli Antiquities Authority you mention is actually a crucial part of being allowed to own the coins - they have to verify that the coins are not culturally significant and release them for travel outside of the country. So, they are playing a very different role than provenance. Heritage recently had a really interesting auction of Biblical era antiquities, and they all had certificates from the IAA which allowed them to be sold in the US.
@Deacon Ray. I really like the idea of a document that comes with a coin purchase that lists everything that the seller knows about the coin and its history, including were the seller originally bought it and any other details. As the coin changes hands this could eventually lead to an impressive provenance. It really wouldn't even need to be an official certificate of any kind just a tracking document.
@Deacon Ray , I really like this idea. It is a nice form of provenance beyond the common practice of keeping all the import paperwork and attribute tags for the coins. Many good comments and suggestions have been offered in succeeding posts. Heed many of them, and you will have a killer Certificate. I would trust actual provenance pieces as much more valuable than slabs with no other paperwork, in my personal opinion.
I often ask sellers for this information. Sometimes they tell me, sometimes I can find it on my own. Collectors are usually more willing to share this info than dealers.
Even "Deacon Ray" has a certain ring to it [no pun intended] that "Ancient Coin Ministry" doesn't. Make sure that people can look up who the real Deacon Ray is. Also some sort of guarantee of authenticity or buy-back if fake during your lifetime and that should do it. Maybe also something on your website showing where interested people can buy books about Biblical coins or Coins as Mentioned in the Bible as well as some basic Roman & Greek coin references. This way you won't have to include the full history of the coin with each certificate. However some basic history of course may be appropriate.