No you should not be taxed on the funds used for college.
These would be gifts to your children and normally gifts in excess of $13K would be subject to gift taxes but there is an exception when gifting funds directly to an educational institution for the recipients education. Basically gifts for education is free from gift tax.
The funds withdrawn from the 401K will be subject to ordinary tax rates though. Just like a regular withdrawal.
Although, withdrawals made for education are not subject to the early withdrawal penalty of 10% (in the event you would be subject to the early withdrawal penalty)
So to answer your question more explicitly, yes you will have to pay tax on the distribtions used for your children's education. Although you will not be subject to gift tax on the gifts made to your children for their higher education.
I trust this provides the answers you were looking for, albiet it may not be the answer you wanted. Please let me know if you have any further questions.