Logic will keep the song arrangement, but that won't help your client, as he isn't using Logic. He will not be able to open your logic project, rather, will need to take the audio files generated by bouncing, as well as the Midi stuff, and build these into a cubase ptroject. Perhaps some screenshots of your arrangement in Logic will help, but you are going to have to write a lot of notes explaining what goes where.
Alternatively, you could ask whether cubase supports open TL and/or AAF and export using these formats. I have been able to open Logic projects exported as Open TL in Nuendo, but there were usually various bits and pieces that afterwards needed to be straightened out, it was less than perfect. The safest route is audio and midi files, but either way he won't be able to just click and open something in Cubase and have a project ready to go as it was in Logic.
kind regards
Mark