Children's savings

trippy

My FIL has left £500 to both of my children and our initial thoughts were to deposit it in their baby bonds/ savings plans for the future. But each child has a different set up:

7yo - Children's Mutual Baby Bond (with Profits) £25 a month (not a CTF) - I can't work out if I can/ should pay the oldest's into the Baby Bond. Nothing on the CM website resembles the plan we have but I think we are already paying the maximum of £25 a month.

4yo - F&C CTF (with just CTF amount in it) and F&C Private Investor Plan £25 a month. From what I can work out, I can simply pay £500 into the Private Investor Plan.

So my main question is what should I do with the oldest's £500 and/or should I do the same with the youngest's so they are both worth the same in the future??? Would prefer to invest rather than sit it in an interest earning account as we're talking about 11-14 years of investment!