I have mentioned in the past, that the adult family fare goes so high (whenever they advertise "free tickets" for kids), as to be even more expensive than comfort flex in several cases, and I've even posted a screenshot or two of the adult family fare being more expensive than even.... Business class!!

However in this particular case, if you do choose dates with the 30% discount on the adults' fare, then that family adult fare is actually in several cases (I think basically every booking class above S or K) even cheaper than... Light! Which I personally haven't seen in a very long time, if ever at all! What's even better is, that since this is a general discount, you can still apply a discount code and save even more €€.

You are correct about the 2x award miles (though since they're not tier miles they're not as significant).
We booked DUS-SKG-DUS at a total fare price of 398€ for 2 adults and 2 kids (not counting taxes) and are due to receive a total 19.328 award miles (1x gold and 3x silver). Had I booked ATH instead, it would have been even cheaper by a significant amount (but I "couldn't" book ATH ​​​​​​).

The only downside is, that these flights fall inside my next gold year, in which I'll need 12 segments and 18k to retain it, so they only get me 2 segments and about 2150 miles, however that's in the very 1st month of that gold year, so at least it's a start...

For FTers I think this is probably not the most attractive promotion, since it's only really good for people with kids under 11.