A total of 7 of us will visit Spain this August. Haven't booked any means of transport from Madrid to Barcelona. Wonder if it is the best choice to travel by train. Wd appreciate any advice on this. Are there several train operators to choose from? Is advance booking necessary? I understand that it takes about 5 hours to travel between the two places. Would like to pick the best cos are travelling with several kids and safety is the utmost concern. Tks for any advice.