For the pears: Use a vegetable peeler to peel pears. Cut in half and use a melon baller to remove core. Place in 4 to 5-quart slow cooker.
Add orange juice and mulling spices.
Stir together wine and brown sugar. Pour over pears. If wine does not cover pears completely, add enough water or orange juice to cover.
Cover slow cooker and cook on LOW for 6 to 8 hours, or until pears are fork-tender.
For the Chantilly ice cream: Place ice cream in blender with grenadine. Blend to combine. If ice cream has not softened enough to blend, add 1 to 2 tablespoons heavy cream.