I just purchased the book based on the 2006 exhibition, "Empress Maria Fedorovna: A Life & Fate" and hightly recommend it! It has numerous pictures as well as quote from Dagmar's diary and correspondence. The book has a quote from Alexander II to Dagmar's father in 1866 when Alexander was sent to Denmark to propose:
When Tsarevich Alexander went to Denmark in May 1866, to propose to Princess Dagmar, he brought a letter from his father to King Christian IX. In his message, Alexander II hinted that he new heir to the throne was less mature and educated than his late brother. The Russian emperor, however, also highlighted the heir's better qualities: "Knowing you kindness and indulgence, I venture to recommend him to you, as I do his bothers Vladimir and Alexis. They are still quite young and inexperienced men, and I am forced to confess to you my fears that, in comparison with our poor Nixa, they may not appear quite so auspicious, particularly out eldest son. I hasten to assure you that our Alexander, despite all the deficits in his development, has a kind heart, is capable of loyalty and one might be proud of him." P. 28
I didn't know the emperor also recommended Vladimir and Alexis as potential bridegrooms as well. Considering how Alexis was MF's favorite in-law and the two got along I would think a marriage between the two would have been quite successful. I really wonder what a marriage between Dagmar and Vladimir would have been.