If you run the potential problems report > Create Problems list then you can select the children who it says were born before the second marriage and then mark as not a problem.
Presuming the children were born during the first marriage the children born before (second) marriage problem is inevitable and I think the only way to deal with it is as above.
Added in Edit: My apologies I am not addressing the root problem of how to enter two marriages with identical husbands and wives rather than preventing the problems showing in a report. Frankly I have no idea how to do this since marriage entry is one-sided, i.e., pick one person and then link them to another and a second marriage of this sort is essentially two-sided. One idea might be to enter the divorce and second marriage as events in the first marriage! but then this does not show up on the Family view screen and more importantly perhaps is not going to take account of any other marriages and divorces between the first and second marriage.