what kind of things were you thinking of? Like a new plant for their home? Or a basket of snacks to eat while unpacking? What other gift are you sending?
Reason I ask, is because I am putting together two housewarming baskets for two friends that are moving, and including necessities (okay, not truly necessities but nice to have nonetheless!) like hand pump soaps from BBW, wallflower scented oil plugins from BBW, etc... I thought I might throw in some basic cleaning supplies, since those are often packed away or thrown out before a move and often needed... Magic Eraser, cleaning rags, etc... disposable camera...
You could do a movie night theme, with rental coupons to the nearest rental place, bags of popcorn, candy, 20 oz cokes, etc so that when they do have a chance to enjoy their new home they'll have something already ready!
Sending dinner over is nice, too, since they are more than likely hard pressed to fix a meal...
I never order things, unless I'm sending flowers or cookies or something, so I'm not sure where to look, honest. I love putting them together myself, and find it to be cheaper.
I recently sent my sis a ton of cookies from Mrs Fields online and they were really nice! If you want to do a snack thingy, they have bunches of different options.