The only Portuguese we spoke when we came here were a few words and phrases we'd picked up from internet sites. Things like: Bom Dia -- Hello; Adeus -- Goodbye; Por Favor -- Please; Obrigado -- Thank You.
I'd get some of them mixed up to begin with -- saying stuff like goodnight instead of good afternoon -- but most people just think that's funny and soon put you right.
Be careful not to get mixed up with Spanish. Portuguese is very different and it could be seen as a bit rude to confuse the two.
English is widely spoken so you can pick up a lot of everyday stuff as you go along. Also, people are very friendly and, if you show you are making an effort and that you want to learn, they'll help you. And there are loads of different types of courses you can do whatever level you are at.
The kids will learn quickly and that's another good reason for you to learn too. You'll want to keep an ear open for what they might be getting up to with their new friends. Mind you, half the time I can't understand what my teenage daughter is saying in any language.
Boa Sorte! -- Good Luck!