I do this too, but have had numerous occasions where MC sends the "Album" to PN but it is not in proper track number order when it gets there.
I've seen that too, but not lately, so maybe it's something that's been fixed.
I will experiment with the playlist sorting idea as a workaround.
You can't shuffle by album in Playing Now, but you can create your own such playlist and send that to PN. For example, add one track from each album to be played to an 'Albums Selected' playlist. Create an 'Albums Playlist' smartlist:
Playlists is any Albums Selected
Shuffle
Expand to full albums
Make your selection, then play 'Albums Playlist'. Alternatively, remove the 'Shuffle' and do that to 'Albums Selected' directly—or put the selected tracks in any order you like before playing the smartlist.
However you do it, the order of the albums will have to be determined first. After the list is started, you will only be able to add albums at the current position or the end of PN. I suppose if you were to always use track #1 to select albums and displayed [Last Played] in the 'Albums Selected' list, that would give you a basis for adding more albums, removing those that had already played, and then recreating the list.