You say IR, so I assume you are from EURope. It seems a hidden surprise for many that about each&any of the old established local state-run national train companies also SELL (as they have done for some 50 years by now) IR as paper pass from those counters that handle INTernational tickets.

If you are british/UK:oBR does not exist anymore, but there are several ticket putlets that offer train tickets to the inhabitants of that island. Check seat61.con or what coms in my mind is ;like Ffestiniog travel.

I think you'd have to exchange your pass for a new one with your children. That costs a bit of money (depending on the option you chose when you bought your pass) but will probably be cheaper than buying separate youth passes for your children (assuming they qualify for free passes).

Hint: Deutsche Bahn also sell Interrail, the paper version, at the ticket office or by phone.