Catch train from ueno-okachimachi

I need to catch a bus to osaka at 10pm (Sumitomo building-shinjuku). When will be the best time for us to leave ueno-okachimachi station.via toei oedo line to tochomae station. we are traveling with 2 older kids , 2 elderly .
After 730pm.... Is the crowd in the train station will be must more lesser. Appreciate you can advise. Thanks in advance

No need so early dep
Ueno-Okachimachi to Tochomae about 20min no transfer.
So dep until 21:00 enough.
Subway[Oedo line for Tochomae] not crowded already usual.

(note)
Oedo line is imperfect loop like this.
http://www.shinjukuhotel.co.jp/img/OedoLine.gif
So you should tale Ueno-Okachimachi[18/above]
to tochomae[0] shorter route train via Iidabashi[12/above].
But detourlow] trains also reached [0] but take long time wrong.