How do you say

I’ve reserved train tickets for three weeks online.

..in Chinese?

我已经在网上预定了三周的火车票。

wǒ yǐ jīng zài wǎng shàng yù dìng le sān zhōu de huǒ chē piào 。

How do you say "My friends and I are planning to road-trip to Tibet during the summer vacation." in Chinese?