while the druid shares the tree-huggerness of the Celtic Druids, the class got he short end of the stick when it comes to "historical accuracy". Shapeshifting wasn't one of their fortes
True, Celtic druids weren't known as shapeshifters (though some legendary figures who supposedly gained knowledge from them were, like Merlin), but that doesn't change that they were cited as a (not sole) source of the class going back to 1Ed. And according to certain legends, they were linked to things like scythes, sicles, spears, clubs, etc., as well as having mystic links to holly, oak, ash, hawthorn and yew...
Of course, this all gets distorted when trasnlated into the world of rpgs.
Whip is probably a good addition, and while greatclubs and longer spears wouldn't be much of a stretch, they'd probably be among the rarer weapons for members of this religious group. Unfortunately, D20 doesn't have a true way to simulate or enforce that rarity other than non-proficiency.