Family car Leon ST or Ocativa / Diesel or petrol

Servus, we are looking for a new car as a family coach. Mainly my wife drives with it short distance (10 km), on weekends are put back as longer routes and we want to drive with it on holiday (2 children). Currently is to choose the Octavia 3 or the Seat Leon ST. Passat is too big, Golf 7 will drive already as 5 door and A4 is too expensive (liked however best 🙂 ) If possible the car should cost around the 15 TEUR, max. 2-3 years old and a as low as possible La Question: – Currently there are many diesels on the market, which are partly as expensive as a petrol engine and often also have better equipment. Does it make sense to buy a diesel with one of the current diesel engines and every year only 10-15TKM? Bzw. where are the disadvantages, except with the tax? Do I have to think about the particulate filter at the moment at short distance? – there are known problems with the 1.2 or 1.4 gasoline engines of the two candidates in particular. Does anyone else have any good advice to consider or an argument why I should choose Leon or Octavia? Thank you in advance