Is it permissible for a man married to two women to take his second wife on every trip, given that the first wife is unable to travel due to childcare, and what is her duty if she feels the husband is not distributing his time equally, and is there a good website about polygyny?

Islam commanded justice and forbade oppression, especially in dealing with wives. The Prophet, peace and blessings be upon him, warned of punishment in the hereafter for whoever does not deal justly between his two wives. Among the obligatory acts of justice between wives when traveling is to draw lots between them. Whoever's lot is drawn, the husband travels with her, and the duration of the journey is not counted against her days of division upon return. However, if one of the wives is unable to travel for a legitimate reason, then the drawing of lots will be among those who are able to travel, and he must appease the wife who did not travel.