With a promo like that, expect that users can't change their birthdate. It won't be highlighted as allowed to edit in their respective user's Profile or Account settings.
And expect a KYC for that to verify the claims. Aside from that, I'm also expecting that the birthday reward will have a wagering requirement before it can be withdrawn and not all accounts are qualified for the reward.
I'm more agree with this compare to a fixed $50.
Freerolls are sometimes awesome as in my casino experience, I yield more profit in free spins compare to a manual spin lol.