Hi and welcome to YT! It's great that you are researching like you are
I think it is probably optimal to wait until your youngest is old enough to understand how "easy" the puppy should be handled. But that might already be the case. I would just say to use your best judgement on that.
Insurance is really good to have but I don't have a recommendation. I know others will be able to help on that though.
Wishing you well on your journey to finding your puppy!