Here are some more ideas. If you go on Fathers Day weekend you can take advantage of the free fishing and save your friend a big bill.
Looking at a two hour radius from Mission I would recommend the Thompson around Spences Bridge; good holes at Shaw Springs, Gold Pan, down from the highway ridge, above the old bridge, top end of town, Martel, and above Ashcroft. The river is open June 1st, my be a bit high at that time but still fishable. Also the Botainy Valley above Lytton, offers some good dry fly fishing (right of the shore) for rainbows in the size you are looking for. Further up the road in the Botainy Valley are three good lakes (Pasulco, Turnip, and Ruddics Dam) all hold coho sized rainbow but access is severely restricted.