hmmm I don't know about your plants, but as far as getting them first, it's best if you show up while there still unloading fish, and buy them before they get out of the bag they were shipped in, that way they don't go into the nasty tanks at the fish store, AND they only have to
acclimate once.
Personally I would try and get them to put a hold on them, for about 3 days or more because some fish just die sometimes, and it's important to get the hardy ones if you don't want to waste your money, if they refuse to hold them, then ask them about there return policies, my LFS is very gracious, and if the fish dies for any reason in the first 7 days after you buy it, you get a full credit for the store, which is pretty awesome.
If they have no return policy and you don't want to risk losing your money, than I would recommend looking online for some with a return or health guarantee, SOMETHING.
good luck.