I'm not sure the exact criteria of receiving a membership card, but I assume you need to have a child in your family that's currently in primary school to take advantage of this offer.
Just register for a card and once the card arrives, enter the membership number in the shofer app to receive 10% of all of your trips. This I believe works even if you use another voucher code alongside the default 10% off discount.
This free membership card doesn't seem to give you access to most offers regular RAC members can claim, but surprisingly the shofer discount works fine.
The card also grants access to a few offers such as 5% off WISH gift cards, cinema vouchers, a few attraction vouchers etc.
New users can also use another existing members referral code to receive 25% off their first ride. I also drive for Shofer if anyone needs more info or a referral code PM me.