HI Brenda, at this stage it sounds like it would be simplest to set this up as a triggered drip campaign.
That said, if you plan on expanding in the future, for example: if someone does something after receiving email 1, 2 or 3, and you wouldn't want them to receive the subsequent emails but instead you'd prefer them to go to another, more advanced "stream", then an engagement program would be preferable since it can pull them into the next stream once they do the actions you were looking for.
Hope that helps in your decision-making, but feel free to write back with any additional questions!