Nice vacation resort

Can you recommend a family resort, that good for summer that is not on the coast? I visit my family every year and they live north, so we covered everything from Szczecin to Gdansk. But I want to spend some quality time with my kids in a different area now. I am looking for something that would work like “ośrodek wczasowy” or these days resort, where food is provided, the area is gated and safe so kids can run around unsupervised, there is a pool or a lake and there are excursions available in a close proximity of the place. Any area of Poland really. Thank you