Never feel araid to tell the truth.

I would love to see those tracks

First--I admire your actions and your thoughtfulness/planfulness behind this question. Second--this is a really tough and challenging question. Third--how to respond if this happens. Wow. Basic principle--don't engage the debate. How? You can try to re-frame and emphasize a different kind of activity: "I was hoping we could just enjoy the trail together and not argue controversies today." You can try to segment the group into self-selecting parts who want to manage the day differently: "Interesting observation--everyone who want to talk about it over here in this group/everyone who just wants to walk the group over there in another group." At this time I can't think of any other defusing non-confrontational approaches...and in these times, I wouldn't advise anything confrontational or non-defusing...even in jest. Good luck!!

You could make a polite, firm comment before you start that if someone's religious beliefs conflict with what you're saying, please refrain from commenting. You could mention that although they have a right to their beliefs, others have a right to believe facts and science.

Pretend he is not there - give your spiel.

When it comes to science vs religion, I really advocate facts over (fiction) faith. If a person finds reality incompatible with their beliefs, that's their problem not mine.

I would ignore any comment that ignored the evidence, an I would be on my knees.... getting a closer look at something so awesome!

Say, "I guess the proto-dinosaurs that wandered around here never read the bible, or they would have known that the earth didn't exist yet."

Maybe point out the preserved tracks and frame it in such a way that it won't be controversial - like:

"It's thought that these tracks are over 250 million years old. Whether you think the world is that old or just 6000 years old, it's still a might long time, and it's awesome just walking along the same trail traveled by creatures so long ago." And maybe add in "Let's not have any arguements about the exact age of these tracks, but just agree they are old!"

The creationist likely knows he is in the minority with his thinking and will appreciate the gesture of you trying to include his beliefs in the discussion. Those are my thoughts, if it was me.

If he tries to debate the geology just resort to the facts. Make sure to verse yourself on the geology and the science involved before hand. He'll either pull "facts" out of his ass - which can be dealt with by a simple reference to "extraordinary facts require extraordinary evidence." He won't really have either. He'll likely have some dope headed and easily disproved hypothesis that proports to explain the observed facts but is so extraordinary and requires so much non-existent evidence as to be absurd.

Either that our he'll just say it is wrong and he doesn't need evidence because his Bible is all the evidence he needs. Either way, you just have to be prepared to walk away from the argument once he looks ridiculus in the eyes of a reasonable observer. Beyond that, there is nothing you can do. Likely, you are right, he'll say nothing.

In a case like that, I would just smile and nod and say "maybe" or "thank you". Then change the subject.

Pointing and laughing can be effective.