If it was during the day, how would he know? It doesn't take long to grab someone throw them to a stake and set them on fire, and I doubt he had Slogra and Gaibon living at her house as her personal bodyguards.
I figured he would have had someone watching over her and his son, after all it was shown that he cared for both of them a great deal back then.
Since he knows he is powerless to do anything to protect them during the day I just guessed that he might have had one of his minions keeping a eye on them.
Maybe his minions were with him due to his assumption that the village his wife and son were residing won't harm them.
Besides, I don't think at that time Drac is powerful enough to gather a troop of willing humans.
Dracula/Mathias at the end of Lament of Innnocence should have been as powerful as Walter, so I don't think "powerful enough" really fits into the equation here since by then he may have even gathered even more powerful souls given that this isn't to far before CV3.
And regarding the minions part, read above to see my reply towards Viskod.