いたしま is incomplete. It must be いたします.
The subjects are different. The guide and tourists will go to Nanzen-ji together, and take lunch there with them, so the subject is "we". However, only the tourists will observe the temple, so the subject is "you". Of course the guide will be also at the temple with the tourists, but he won't observe it. If いらっしゃいます and なさいます are used instead of 参ります and いたします, respectively, it sounds like only the tourists will go to the temple and take lunch without the guide.
Another interpretation that 参る shows the respect to the temple is also valid. In fact, お寺に参る works perfectly fine as a common collocation.