I know Tammy will come up with all the info on golf, as I do not have exact prices - but we have 11 championship courses out here, including Nicklaus and Norman courses. Most are Crazy Expensive.... The most beautiful to play are Cabo Del Sol and El Dorado.
The least expensive is The Raven Golf Course at the CSL Country Club - however it is not an ocean course.
Most if the courses have better 'twylight' rates - but that kind of defeats the purpose of a day activity. -
Plan on spending 200-300 for green fees.
Suggestion for snorkeling would be The Tropicat.
TROPICAT CABO SAN LUCAS SAILING JAZZ CRUISE CATAMARAN - it is a huge and sturdy catamaran with very nice amenities, great crew and a super fun day for all.
Also try Pez Gato CABO SAN LUCAS SAILING PEZ GATO
You can reserve online with both.
JT WATERSPORTS has Kayaking, Jetskis out of the beach at Melia Cabo Real on the corridor, or Medano Beach in Cabo.
Janet's suggestion of Ziplining is great also - I know they really enjoyed it.
Sounds like your guests are going to have a great time!