If they thought he was guarded, plus if they thought Dubai authorities were providing security, it would need at least three or four people, possibly eleven. They would have to spend some time watching to assess his security. The woman might have been there to stabilize the men (if they were not experienced). The tennis thing might be to help them blend in if it was a hotel with a tennis court.
Pope Francis: Divorced Catholics who remarry and their children deserve better treatment (AP)
from the article: Hamas man's Dubai death was a Mossad-style execution