Hi Lauren! Good to know for you (and me) that there are many more families struggling with the same thing! My two girls of 3.5 and 1.5 are learning three languages since they were born here in Sydney Australia. I speak to them in Dutch, my husband in French and they learn english from friends, daycare, tv etc. As my youngest is only 18 months old and saying some words only, it's obviously best to now only mention what we do with our eldest daughter. She has gone to daycare two days a week since she was 6 months old. She picked up english words at daycare and then increasingly from singing songs and watching cartoons or other kids's things on television like Pocoyo, Olivia, The Wiggles etc. She was at three years old putting a few words together, mainly in Dutch but then also some in English but she's also come out with these "key phrases" that she simply memorised from either something she'd heard repeatedly in her favourite cartoon or from a book.
Coincidentally, at her daycare I also had a chat with one of the teachers who equally mentioned to maybe talk to her in English so she could communicate better with the staff there and the other kids. As much as I did understand her point of view, I didn't want to do that so I didn't change much of what I was doing with her. What I did do though and this might be of use to you, is that when we were going out for walks, my daughter and I, we were going over the things we saw around us and I'd ask her what it was called in Dutch, English and French. It became a bit of a game. So that way, her english vocabulary did expand but I wasn't really talking to her in english but merely asking her what people would call something in English. I thought that was a good compromise and am still happy with this. Cause my daughter definitely associates persons with languages so I stuck to the One Person One Language thing which is what is advised on this forum I think.
Since she turned three I find she's playing more with other children and perhaps because of that she is talking better but honestly I think it has more to do with her development. Her language has really taken off in the past 6 months so perhaps that may be the same with your boy. Besides, English is so easy! So much easier than French, Dutch and in your case, Portuguese!
Btw, when playing with her sister, she often talks in English or a mix of English and Dutch. I think she picks the English cause it's easiest and also because most times when she plays with friends or when she's in a playground, english is always the spoken language around her.
Like your son, my daughter is also a bit of a shy girl. Part can be simply her character but I also think language is a big thing. I disagree that is it because she realises she is delayed. I don't think a three year old has the capacity to analyse it in that way. It is more the parents that worry about it all! I constantly wonder how things will go in the future with the three languages. But it is true that as her english improved, she was able to answer people's questions a bit better.
She is still and will be for a while, behind in all three languages. Obviously, learning three AT ONCE is just a big stretch. But in the long run a great achievement so I am sticking to it! What I did decide already though is that I will probably not bother too too much with reading and writing in Dutch. I will do a bit but I think it may be too much for her to learn the Dutch language in depth. Especially if we stay in Australia and she needs to learn and write perfect English and French. But I do want her to be able to communicate with my family over the phone and in person and then the spoken language will do. Oh well enough time to decide. What are your thoughts on it for your son?
A major difference with your son however, is that my daughter is attending the french australian preschool here in Sydney since August. Teachers talk in french but her french remains her third language (first being Dutch and second English) unfortunately because there are many non-french speaking kids in her class! But that is likely to improve over the years when all learning and reading material will be in french so I don't need to worry too much about that I guess. My husband is very frustrated though how she keeps talking to him in Dutch and English ;-) Patience is very much required! And I don't tend to have much of it.... but this is our decision to raise them trilingually so we have to stick to it, encourage her as much as we can, teach a lot and be patient.
Ok with this I will end this email. Dear me, I didn't think I was going to write this much!! Reading back over it, I may have rambled on a bit. But if some of it is of good use to you then great!
Good luck with it all. Do know that you're not the only one!!