I wouldn't consider 4 or 5 buy-to-let properties as 'small scale'. That's a €1 million portfolio, so unless you have €5m-€10m of other investments in your back pocket, this is a big deal.
I strongly recommend you do some serious financial analysis and get independent professional advise from someone who has no vested interest in this matter before you proceed with this deal. I heard the retiring CEO of IIB Homeloans on the radio yesterday saying that there was no value in Irish property today. Have you considered the risk of a property slump? Are you putting your home at risk to fund the deposits on these properties?
But to back to your original question, I'm not sure why you would want mortgage protection/life cover on each property/mortgage. If the worst came to the worst and your family were unwilling or unable to keep up the investments, surely they could just flog them off? If you want to buy an extra €1 million in life cover, why not just go out to the market & buy it - Why link it to your properties? I know there may be a slight tax advantage, but even this is going to have negligible impact in the early years when your mortgage interest will be high.