i am going to guangzhou but staying at 2 places.

When i arrive in china, i will be staying at my relatives for 2 days and then i will be attending a cultural,martial arts camp for three weeks 21 days. And then once the camp is finished i will be returning to my relatives and staying there for 1 week.
For the letter of inviation, can i just use the one the Camp will give to me or will i need them to state i will be staying in china for a few days before and a week after at a different place. Or do i need 2 letter of invitations. One from the camp and one from my relatives??
The only play in china i will be at is Guangzhou.