In order to be able to attend the Race, you need to be online. After you attend the race, you can get offline. For the contributions you make OFFLINE to be counted, you need to MAKE SURE to connect your game to the internet before the Race ends. Otherwise, they'll not be added.
If the player changes Club while the race is active or joins a new Club during the race, he/or she won't be able to join the ongoing race.
Club members that have "0" contribution won't be able to get the League rewards even if the Club wins them. Members who have contribution scores higher than 0 get the rewards.
If all the members of the Club are not playing the game for a while, they'll be counted as passive players. This club filled with passive players will not be able to join the first race that is active once one of them plays the game when they come back. They will be able to join the race after the currently active one.
If you open the game after a while and you have unclaimed Club gifts, you'll them.