I observed most sub board have no recorded post for a while now, and to the best of my knowledge, I suggest that there should be only two sub boards at the child board due to the following reasons:

Mining:  the discussion about mining in the  mining board should be brought to the main board or the regional language board. The mining board hasn't been active for a while now

Market place: I don't think this local board need a market place as it might become a catalyst and a good opportunity for scammers to operate since our profile are still anonymous, you can't hold anyone responsible for your mistake.

Press and news from India: I think the news from the press can be discussed in off topic or the regional language board

Altcoin : altcoin can be discussed in the main board and also the regional language board, I have seen cases where this happens in this forum.

Buying and selling: should be discarded for security reasons because it might tarnish the reputation of our board if any trade turns out to be scam.

The only child board I recommend to be left out are the off topic and regional language board as other board discussion can also be discussed in those two boards. The Nigeria board has I good number of active user and they are doing fine with only their main board.