1. Shall we fix a date for the picnic?
我们定一下野餐的时间好吗？
还能这样说：
Shall we appoint a time for the picnic?
Can we set a time for the picnic?
应用解析：
be no picnic 有困难或麻烦，不是轻松的事。
例如：Travel abroad is no picnic.
海外旅行可不是一件轻松的事情。
2. If the weather is fine, we are going camping this weekend.
如果天气好的话，我们周末去露营。
还能这样说：
If it is sunny, we decide to go camping this weekend.
Why not go camping this weekend if the weather permits?
应用解析：
the finer points of sth. 只有行家才能领略和欣赏到的某些方面和细节；
get sth. down to a fine art 学会将某事物做得尽善尽美
3. Let's meet at the gate around two o'clock, and not leave without seeing each other.
咱们两点钟左右在大门口碰头，不见不散。
还能这样说：
We will meet at the gate around two o'clock. Be there or be square.
Let's make it two o'clock at the gate, and not leave without seeing each other.
应用解析：
between you and me and the gatepost 严格保密；
a gate of ten thousand 万人观众；
gate sb. for sth. 惩罚性禁止（学生）离校
4. After April, we've got to make time for the picnic.
4月以后我们还得留点时间野餐。
还能这样说：
After April, we need to leave some time to picnic.
We need to save some time for the picnic after April.
应用解析：
make do with sth. 用某事物勉强应付；将就；凑合。
例如：We are in a hurry so we had to make do with a quick snack.
我们时间很紧，就胡乱吃了顿小吃。