Travel / From Warsaw to Wroclaw with kids? [3]

Sorry, my english isn't very good...

We are going to visit Wroclaw next week. Our flight will arrive Warsaw airport at 8.30 on Sunday morning. What is the easiest way to get to Wroclaw? I think the cheapest is by train? We should take taxi or bus from airport to railwaystation? The biggest "problem" is that we have two little kids (ages 2 and 3) with us. It won't be very easy to carry kids and luggage to the bus and to the train... Can little kids travel free by train? LOT flight from Warsaw to Wroclaw isn't very cheap. Is there any cheaper flights? How long it takes to travel by train from Warsaw to Wroclaw? It would be nice if someone could give me some tips travelling with kids in Poland.