Coming into this rather late, but the question asked was what happens to the pension after he dies, whereas most of the answers seem to relate to his demise prior to taking the pension.
Prior to taking his pension he should be contacted by the Administrators/Trustees giving advising him of the options available under the terms of the scheme. These may include:
a) equal payments until his death;
b) a lower starting figure with annual increases allowing for inflation;
c) a tax free lump sum, again with lower starting pension payments as in options a & b above;
d) a lump sum to purchase an annuity from another provider.
If he were married there may also be the option to take an even lower pension under options a & b above, with either a half or one third pension being paid to his spouse, from his death until her demise.
I have not heard of a child being able to receive payment under the terms of a parent's pension, especially due to the longer life expectancy of a child, except where the the terms of the pension include payment for a minimum period and the pensioner dying within that period (the residue of the pension payment being paid to the pensioners estate). Naturally my information may be out of date due to the vast number of changes that have been made to pension schemes in the last few years.
If the value of his pension fund warrants it, I would advise him to speak with an Independent Financial Advisor to discuss his various options.