I'm not very sure how you select which view to display, but here is some code to iterate through the views of the current document in your MainFrame:
EDIT: modified code for MDI
CMDIChildWnd *pChild = (CMDIChildWnd*)GetActiveFrame(); // EDIT: added line
CDocument *pDoc = pChild->GetActiveDocument(); // EDIT: added pChild->
POSITION pos = pDoc->GetFirstViewPosition();
while (pos != NULL)
{ CView* pView = GetNextView(pos);
// if this is the view you want to activate
// pChild->SetActiveView(pView); // EDIT: added pChild->
}