"I don't think you'd better consider..." sounds a bit clumsy to me. It almost smacks of a double negative (It isn't, but you have to take a nano-second to confirm that). I would phrase it as in your second example, or, even more simply and hence more effectively, as "I don't think you should consider..".
Because "I don't think you'd better consider..." is clumsy phraseology, I feel that it loses much of its force in persuading Father.
Whether it can be construed as any form of threat would depend entirely on the context
Interested in Language