Questions regarding druids and spell caster mitigation

I am working a Paizo campaign (Kingmaker) and Ihave a few general PC handling questions. Without making this a boring no-fun-fest for my players, I have a few questions on handling lvl5-6 spell casters.

1. Can druids cast spells while using beast shape?
2. How do you mitigate or remove a spell caster from combat without trying to kill her?

Some PC common tactics: The PCs cast detect magic to determine magic traps/magic items on NPCs/possible loot locations.Then they entangle or glitterdust those areas/items.

I'm all for letting my PCs setup ambushes and awarding them for good tactics, but the challenge has been reduced.

Spell casters in this group/lvl: Druid (6), Warpriest (6), Wizard (5)

Suggestions?