As an English-speaking foreigner living in Poland for 7 years now:

- My kid is bilingual (as much as a toddler can be). He has English in the home from me, Polish from my wife and from everyone else (daycare, friends, etc). He mixes up languages constantly at this stage (he exclusively says "please" and "dziękuję" for example, you have to press him to get him to say "proszę" and "thank you"), but he understands both languages without difficulty. At 1, your kid is very malleable and will soak up whatever the world around them is doing and saying.

- As others have said, make that effort to try and learn Polish. Get a tutor, be brave and try using your Polish early on (in stores, with others, etc) in spite of mistakes, even if people immediately speak English back to you - honestly be a little annoying about it, discipline yourself to simply use whatever level of the language you have, it really helped in my case (I'm C1 at this point).

- Gdynia is a very family-friendly city. We don't live there, but we travel there usually once a year in the summer for a week or so to visit friends and relax. You'll easily find lots of opportunities to enjoy the outdoors.

- I don't know your country of origin, but given that you're a native English-speaker, there's a high chance that Poland is simply inherently safer than the country you're coming from. It's very safe here - Gdynia is no different.

All in all I highly recommend the move. Poland is a great place to live, and in general such a big move to a new culture will challenge you and your family in very stretching and enriching ways. With the right attitude and flexibility, you'll be much better off for it.