Challenging players with a wizard encounter

[Mage Evolving]

I have a group of 5 players who are in the midst of an old school D&D campaign that I am modifying for Pathfinder. I am looking for ways to make their encounter with 2 hostile Wizards and their pet velociraptors interesting and challenging but not impossible. Both wizards are slated to be evokers.

Any Ideas?

[pachristian]

Make sure the wizards are screened; players should not be able to reach them easily. Give the wizards a chance to set up defensive spells before they engage PC's.

[meabolex]

Use terrain to your advantage. Make the wizards have a high-ground position. If the PCs try to reach them, make them pay (walls, rough terrain, slow, etc). If the PCs fly, dispel their flight. Assume the PCs will use archery and have a wind wall in place.

Make sure the wizards are spread out.