I think it will make a nice, full mass planting in that space. Those kind of Mediterranean herbs will grow with very little space and poor soil in their native areas, so I would think they'll do fine. If you want to plant other things with them, then yes, you need to move a couple of them elsewhere. But I really think it will look great just as a little bed full of white lavender. No room for weeds either!
I imagine next year the flowers won't flop and they won't look odd to you by then. They're just babies with weaker stems right now.
