In my personal opinion, I think that real life examples would be better and easier to understand than scripture examples. Yeah, your audience might understand that Jesus multiplied fish and loaves of bread for a whole crowd to eat, BUT I think your students would relate more to using everyday life examples: Jimmy likes eating bread.
As far as how to go about teaching past tense, I would start off introducing simple past tense verbs. Meaning, verbs that only require verb+ed and slowly start introducing the irregular verb (speak --> spoke). You shouldn't totally ignore the irregular verbs because there are about 170ish of them and a lot of them are basic verbs the students will need to know: ride, drive, hear, etc.
As for activities and games, I've got a couple up on my site -- JHS Grammar Verb PastTense
. The games are geared for Japanese students but they can easily be tweaked for your students.
I know that doesn't help you too much but it should start you thinking in the right direction.