Thanks all - Guide books have arrived (Lonely plant and rough guide) Our flights are actually in and out of Xian (would have opted for in to one place and out of another but got a deal where even adding in an extra internal flight was worth it.
Plan today (may well change after your input and reading books)
Xian 2 days (warriors,muslim quarter, cycle walls)
Xian to Beijing on overnight train (Kids very keen to sleep on a train)
Beijing 4-6 days including possible overnight near more remote great wall destination. Like the sound of the lake 88mph
Beijing bullet train to Guilin (Husband and son fancy this experience!)
Guilin /Yangshuo area 4-5 days(river trip ,raft trip, terraces,walks,cycling)
Guilin late flight to Xian , Xian full last day (pagoda or trip to mountains)
We have in 17 nights in China so have some time to play with or add in more like Chengdu. We are not intending to go to Shanghai.
I have noted that visa's are expensive Thanks Spiderpants and will get some fetching facemarks Seatoski.
Bubbles are not put of by toilet situation - some good tips though noted.Have done DIY trips on a budget to quite a few places where English not spoken much ( India, Nepal,Uganda, Malasia, Thailand, Costa rica) and have been to Hong Kong.
As my husband and I have got older we are more likely to mix up the backpacker style with an organised tour company for specific things. Shanghai diva thanks for clarifying the car hire is with a driver - phew , and a good idea to do this (also heard this recommended for getting to the less touristy parts of the great wall.)
Really helpful to know the haggling etiquette as it does vary in different cultures.
Would like to catch some Chinese opera (Daughter studies music) some acrobatic/circus stuff and poss some martial arts demo type vibe.