Both fabrics are so cute that I'd use muslin on the back and make two quilts. I'd follow the dashes on the pink one and also make new dashes around all of the other "undashed" figures - that would give you the meandering effect without ruining those little bunnies etc. Dark brown thread would be my choice.
Not sure about the green fabric but it is so pretty that it might be compromised with a different pattern on the back.