Well, one of my does rather consistently kindled around day 34-35 her first years, today was day 30 and I think it'll take a few more days, still eating well and digging, quit likely there'll be easter bunnies.
All I do is making sure they have enough calcium when the time comes, feeding quite a lot of dandelion if available and putting a little ground up egg shells on their food, an option is to offer them a Tums (fruit flavoured is said to be accepted quite well)
I'm not sure about lavender, don't know of positiv effects in that situation, but it's of the mint family and mint is something I would definitly avoid with pregnant or lactating does.
EDIT: Well, read up a little, mixed opinions out there..., if it really helps to get things moving and your doe has a history of problems, it might be something to consider, although I think the power of such plants gets quite overestimated anyway.