Hello Monmon,

What I think you can say is:

Nǐ máng ma, wǒmen zǎoshàng kěyǐ bù kěyǐ yīqǐ chī zǎofàn ma.

你忙吗，我们早上可以不可以一起吃早饭吗。

Nǐ máng ma, wǒmen wǔshí kěyǐ bù kěyǐ yīqǐ chī ma.

你忙吗，我们 午时 可以不可以一起吃午饭吗。

Nǐ máng ma, wǒmen wǎnshàng kěyǐ bù kěyǐ yīqǐ chī zǎofàn ma.

你忙吗，我们晚上可以不可以一起吃晚饭吗。

In the morning you have breakfast 早饭, in the afternoon lunch 午饭 and in the evening dinner
晚饭, I presume.

But of course Benny will tell you exactly how best to say these phrases.

Succes

万事如意

陆蓝克