I would be interested in teaching adults or conversational English preferably online, and I have also considered teaching in a preschool.
That's two very different types of student and two very different types of teaching. I'm wondering what the rationale is behind it. Do you feel drawn more to one than the other and if so why? Don't make the mistake of thinking that small children are easier to teach, they're not, if anything they can be far more challenging as they grasp concepts completely differently. You need solid training in early years education to deal professionally with pre-schoolers.
One thing you should be clear about is that teaching in Polish public schools is not at all well paid so you should be looking at private establishments.
However as Delph points out there are opportunities in private, international schools at every level from kindergarten/pre-school up. He is also right that as you are planning on moving to Poland permanently you should invest your time and money in getting general teaching qualifications that will form a strong base for a decent career in the education sector in Poland.
One thing to consider is where in Poland you'll be moving to, If it's a rural area or small village/town then you might have to re-think your plans and go the online teaching route, but good qualifications are always worth having.
I see a problem though with your timing, as the next academic year starts in Sep 2018. You might be too late to apply for this year and a B Ed would take three years to complete but if you can start in Sep, you'd finish in the summer of 2021 which should be ok.