Hello and welcome to col
I would definately let him settle in first. New home, leaving mum & siblings etc., can upset a pup's tum anyway, so best to wait a while before giving him treats to make sure he is ok with his new environment. Particularly if you are a bit concerned what treats to give, if they do upset him you won't know what is causing the upset (new home/food/treats) iyswim.
Following on from that - when you know tum is ok, I would expect the packets to say the age that the treats are alright from.
I am sure members will be along shortly to give more advice and what is best to avoid. MInstrel likes Fish4Dogs all stars training treats and they seems to suit his tum, but there are many others available. I think treats with lots of salt content are best avoided.
Warning: I am probably being a bit over cautious in advise as my pup had a jippy tummy from the start