A stock in my minor sons name was bought out last year. I received a 1099b for $2700 even though I received new shares not cash. Now it's worth less than the cost basis. Is there anyway not to include the full amount in my return or should I file a separate return for my 16yo son. Thx

File a separate return for your son.

Even without his personal exemption (you are going to claim him), he will likeky owe zero taxes.

The stock bought out last year were sold for $2700. Based on your cost basis, you have loss or profit.
For the new stock your cost basis is $2700.