My Daughter And Son In Law Have There First Child,
A step by step approach needs to be taken
Detailed Answer:
Thanks for using the Ask a Doctor service.
I understand your concern. It might be difficult to counsel your son-in-law but you need to politely explain to him that we need to go one step at a time. First the child will be able to sit, then stand, then the child will start running. It is not possible that the child will start running before the child can sit. So, he (as a father) needs to hold onto things and be patient. Assure him that the child will be tough, but only when time comes.
As of now, let me assure you that swaying or even hanging him upside down for brief periods of time would not do the child any harm. Nevertheless, tell him (the father) that he is still a baby and his body might still not be equipped to handle the pressures as yet. Reassure him that with time surely the child will be able to handle any forms of stress, but now is not perhaps the best time.
If you present it in this manner, I do not think that it will appear to be a big deal.
Feel free to write back.
Regards