I am from Spain, and I have a 4 year old daughter and 6 year old boy. They were born in Spain, but we moved to the US 2 years ago. My husband is american, but speaks spanish very good. We use hte ML@h model, speaking spanish at the house always between us, we all talk in spanish, and no english allowed in the house, that is the only way we found works for us, so the children speak spanish, english, they are going to learn outside, no matter what!!! Some people, do not like that model, because my husband talks spanish wiht an american accent, ...or because it took a little longer for the kids to speak english perfect.... but now is amazing how they know to talk to us in spanish all the time. Still, my american husband, reads the School books with my son every night, he has to read 30 minutes for homework everynight, and of course, is english!!! So, you with your todler, do that, and your Argentina husband can do the spanish books, and your little one will enjoy as much one and the other, with time, If your spanish is pretty much, OK, I would recomend you do the Mother Language, at home, in this case, the father language, because they will learn english sooner or later too. I have a french friend that speaks french to her girls, but is very rarely that the girls respond to her in french, because she is the only one that talks french to her girls, the american husband, does not speak french.
Enjoy your bilingual family situation!!!Try to stablish what would work best for your family, every situation is different, this is what worked for me, I just wanted to share it. I am very thankful to my husband for helping me with Spanish at home....... But my daughter melts down when he sings the Sun SHINE to her everynight!!! ITs great.Good luck
Live in US, born in Spain