I want to simplify travelling as much as possible due to the children. My husband thinks the train is a bad idea. He insists Tata will come pick me up. He seems to think it wouldn't be safe?
Travelling on the train would be perfectly safe if you stick to TLK/Express/Intercity trains.
It's not exactly complicated to get from Gdansk airport to Koszalin. Taxi from airport to Gdansk train station. Train from there to Koszalin.
Here's an English language search engine for Polish trains: rozklad-pkp.pl/?q=en/node/143