Can a child of a deceased participant in a 401(k) plan Rollover the money to an IRA or must they take the entire distribution.

It depends upon what the Plan allows for distributions. It may not allow anything other than lump sum distributions for beneficiaries. If it allows annuities, then 401(a)(9) governs who is eligible to "rollover" to an IRA. Anyone else add anything?

Actually, it's 402© that governs whether a distribution may be rolled over. That section provides for rollovers by employees, or by surviving spouses, but not by other distributees (such as children).
If the distributee is otherwise eligible to roll over (i.e., an employee or a surviving spouse), then 401(a)(9) may come into play, since a required minimum distribution may not be rolled over by anyone.

Correct, I misspoke. 401(a)(9) does not govern the rollovers, but the required minimum distribution patterns.

The main point as indicated in jashendo's post is that a child cannot rollover the distribution.