Praise be to Allah.
There is nothing wrong with meeting to organize useful lectures and some other good and permissible kinds of activities.
We ask Allaah to help those who do these things to do that which He loves and which pleases Him, and to bless their efforts.
With regard to the sporting activities that you mentioned, if it is possible to do them during the day, that is preferable, because talking after ‘Isha’ prayers is makrooh, except if that serves a purpose. But if time is short and the aim is to provide relaxation so that the people can focus on the lectures, then there is nothing wrong with it in sha Allaah. See also question no. 20811.
With regard to qiyaam al-layl, gathering for this purpose is not prescribed, unless:
1-That happens occasionally and is not something ongoing
2-It happens without prior agreement
But in Ramadaan it is prescribed to pray qiyaam in congregation on every night of the month. See question no. 38021.
Ibn Qudaamah (may Allaah have mercy on him) said in al-Mughni (1/442):
“It is permissible to pray voluntary prayers in congregation and individually, because the Prophet (peace and blessings of Allaah be upon him) did both, but most of his voluntary prayers were offered individually. He led Hudhayfah in praying a voluntary prayer once, and Ibn ‘Abbaas once, and Anas and his mother and the orphan once, and he led his companions in the house of ‘Utbaan once, and he led them during the night in Ramadaan three times. These reports are all saheeh and jayyid.”
The naafil prayers offered in congregation in these ahaadeeth took place without any prior agreement. Hence Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said:
“With regard to a group agreeing to meet on a certain night to pray qiyaam al-layl, this is bid’ah, because praying qiyaam in congregation is not prescribed, unless that happens occasionally without prior agreement and unintentionally, as happened with the Prophet (peace and blessings of Allaah be upon him) with ‘Abd-Allaah ibn ‘Abbaas (may Allaah be pleased with him).”
Fataawa al-Shaykh Muhammad ibn Saalih al-‘Uthaymeen, Kitaab al-‘Ilm, p. 208.
So our advice to those who organize such activities is either to limit it to lectures and other activities, or to leave some time for those who want to pray qiyaam al-layl, and let each of them pray individually.
And Allaah knows best.