Am I correct in that your tank is 6 to 7 days old? If so, don't add anything else. While crabs and snails are cheap, they will not survive a cycle (which has yet to have happen at 7 days).
Once cycled, Reefcleaners is great but understand that you will likely get A LOT more than you order. 5+ times the quantity you order is not unheard of with them. While this is nice, you end up with way more than you actually need. If your LFS will give you a little credit for the extras go for it, if not you may just want to buy some individuals. Snails of all types/sizes are $0.99 each around here.
Snails, crabs and other inverts should be acclimated slowly (starfish even more so) but once acclimated they are fairly durable (except when a hermit decides it wants a snail's shell
).