wa alaikum us-salaam wa-rahmat ullaahi wa-barakaatuh
All Praise be to Allaah.
First of all, we pray that Allaah hastens with blessing your generous and considerate father with the guidance of Islam, for indeed He is The All-Hearer, and the One who grants the requests of His worshippers. It is incumbent upon you to invite him to Islam and show him and explain to him the light of truth. Your should solicit the assistance and participation of your husband in this effort as well.
Second of all, regarding the ruling on eating the meat found in non-Muslim countries, please refer to question # 103.
Thirdly, a Muslim should be clever and sagacious in choosing the appropriate words and gentle-mannered approach to inform such a kind person of the place where one can buy "halaal" meat. Since he is already spending money on the meat whether he buys Islamically-slaughtered meat or otherwise, your guiding him to the appropriate place preserves the benefits and interests from all facets, i.e.: not refusing his gift; and achieving the permissibility of eating the meat. In fact, it would be a wise idea even for the meat he buys for himself and his house, as it will be better and healthier. Perhaps you could approach him with the idea as a suggestion and not as a firm requirement, explaining to him the reasons behind it both from the point of view of the Islamic shari'ah as well as health reasons. Thus, it would not be something you are presenting as forcing your opinion upon him; rather, you would express the importance of the issue for you, while at the same time complimenting and praising him for his generosity, expressing your embarrassment for having opened the subject. I would expect such a generous man to accept a well-mannered approach, don't you think?