These things come to mind:
1. Use Carbon Copy Cloner to copy the originals to an external drive (partitioned). Reverse the process with new SSD. Or put new SSD in external case, and copy directly across, then install new SSD.
2. Make disk-images of originals (see Disk Utility.app). Move to external drive. Partition new SSD. Use Restore feature of Disk Utility to read disk-images. Or mount each disk-image, and use Carbon Copy Cloner to copy from image to SSD partition.
3. Make disk-images as in #2, but upload files to a storage service. Partition new SSD. Download one image, copy it into place, delete it. Repeat for 2nd image.
There are probably other ways of doing it, and other tools than CCCloner. It depends on what other external drives you have available to you.