At the outset, I would like to express my thanks and gratitude to all of you for undertaking this historic tour, for taking the trouble of coming all the way down here to have a first hand knowledge of/ about the situation on the ground.
How can I greet a visiting team of human rights activists in a polite manner in a formal meeting? Does the above sound okay?
I would like to express my thanks/gratitude [choose one; they are synonymous] to all of you for undertaking this historic tour, for taking the trouble of coming all the way down here to gain first-hand knowledge of our situation.
I don't think 'on the ground' is the appropriate idiom-- presumably any competent team of activists is already 'on the ground'.