yes, I think you should let them get visa before you go back.

You do not have to mention you cannot go home or whatever. To attend your graduation ceremony is a good excuse, if not, you can always say "to travel in the States and to visit my daughter", which is proper and understandable.

Mail your documents (copies of passport, I-20, I-94) back to your parents. If the I-94 shows you have not left US since your last entry, I do not think the visa officers can figure out. But I think it is a safer and better arrangemen to let them get visa before you go home.

I hear it's easy to get visa this year. Good luck.

欧上次是这样操作的: 欧先在墨西哥弄了个反美签证，然后让父母在中国签证，欧给他们的材料里没有包括刚弄到的最新签证，好像前征管也没有查出来就给他们签了。这样我们双方都拿到签证后，欧去买了欧的往返机票和他们的来美机票。

当时也有点担心双方同时签证的问题，不过好像他们没有查，而且其实回国然后再带父母过来玩本来就是正常的，没有违反什么政策把

我感觉他们不会查的，但是我上次和父母是在两个不同使馆，你在同一个使馆，我还真不是很sure. 不过我觉得很少会因为子女要回国而拒绝父母赴美的。倒是你自己，如果是敏感专业什么的，要不要考虑先弄个签证再回去。