You will find a lot of information on pedals by doing a search on this site. This topic has been covered at length.

I like Shimano M324 pedals, use SPD cleats on one side, normal shoes on the other.



But, you might want to start with the same ones you have used on road bikes since that is what you are used to. And plan on normal shoes for the campsite.

Mountain bike shoes are better for walking than the road racing ones, so you might want to eventually switch, but no reason to invest in new shoes and pedals right away.

A friend of mine uses only one pair of SPD type sandals for everything when touring, he leaves the shoes at home. But that is not my preference.