Any legal people? Can you witness to a will if your children are beneficiaries?

[BlueBloodedBlue]

I know you can't benefit yourself, but not sure if a witness's child/ren can be a beneficiary.

No

No. You need 2 witnesses who cannot be beneficiaries. They both need to be in your presence when you sign the will, and both witness it together.
The executors can be witnesses though.