Is the second wife entitled to refuse the gathering of the two families for food and prayer, and to refuse feeding the children of the first wife in her apartment, and what is obligatory in financial support between the two wives to achieve justice?

You do not have the right to compel your two wives to eat together or for each to serve the children of the other. This is because obedience to you is not obligatory in these matters, due to the harm that it may cause them. As for financial support (nafaqah), equality between the two wives is not a condition; rather, what is obligatory is to provide for each of them according to what is customary (bil-ma'ruf).