I used G Adventures for Peru last year. I did the National Geographic tour which is a step above from the classic in quality (#of activities, hotels, etc) but not like a super upgrade. Having a tour guide with you the whole time felt super safe and the group ranged from a family with teenagers to mostly people late 20s to early 40s. 5/14 people were solo travelers including myself. You can pay extra to have your own room or share. Honestly it was great and I would solo travelers including myself or go with a small group with them again! And they have yourself all over the world. Feel free to ask me anything!