Hi Mandy,
So, on this trip there are a few religious sites that you will visit and yes, you will need to dress modestly. The most disciplined in enforcing the dress code is the Church of the Annunciation. Generally the rules are;
Covered shoulders (t-shirts are ok but no vest tops)
No cleavage
Skirts at or below the knee.
Some ladies choose to wear a scarf to cover their heads. Also, some ladies carry a sarong to wrap around their bottom half to cover their legs. The Tour Manager should advise the group the evening before which sites they will be visiting the following day so you can dress/be prepared accordingly.
At the moment there are 12 of you booked on this tour - I'm sure you're going to have a great trip.
Kindest regards,
Julia