I wondering a bit about your question . . . will someone be at your house to pick them up once they are delivered? Or will they be sitting out for quite some time until you return home?

If someone will be there to accept them (and depending on low temps at night--anything below 30, absolutely not), you can place 2 of the 40-hour heat packs in with the animal (one on top, one on bottom) and they should get there OK. Again, use this ONLY if someone will be there to accept them for you and get them into a nice warm tub/cage right after they arrive.

If no one will be at your house to accept them, then NO, do not attempt.