Instead of saying "Would you roll over and say okay, or would you put up an argument?" you should phrase it more honestly with "Would you honor the agreement you made, or decide to pick a fight over not getting your way?"
You agreed and yes, it's free, but it's still a new snake and it will have expenses in food and bedding and such. It will take time to care for. Also, it's one free snake in a virtual sea of free animals that will continue to be available for many years, because there's always someone who gets a pet and changes their mind later on.
What if you get the free snake and then find out it needs vet treatment? What if it's got parasites and you have to treat it AND treat all your equipment? How much will you need to spend on it? How much of a budget did you agree on for vet treatment for your pets?
You have the rest of your lives to live together. Breaking an agreement just before you two have a baby arriving isn't a great idea. Getting pets just before a baby arrives isn't even a good idea.
just my two cents.