As a PhD student, can my name be included in a research grant to protect my ideas?
While it depends on your region as well as the specific grant to which your colleagues are applying, I think you are approaching this issue the wrong way.

It is true that after working very hard on a certain field, subject or method, we may become overly attached to the ideas that we generate. However, if you are not willing to accept (and even embrace the fact) that other people are so interested in your work that they are using it and, more importantly, submitting grants on it, why are you even concerned about publishing what you do?

More importantly, they should (and likely already have, given that they are asking for your help to write the proposal) realize that you are possibly one of the most capable persons to work alongside with them on the topic, given that it was you who initially proposed the idea. You can benefit from their grant by collaborating with them -- perhaps by providing guidance to the students who they are willing to hire to work on something you value important!

As someone who collaborates with many other people who work on ideas that I initially generated, here's how I would approach the issue. Tell them which particular research directions you would like to work on yourself (perhaps as a part of their grant, trusting that they will fund you if the grant is funded), and offer your expertise to them on additional directions that they can have other people working on. On those latter papers perhaps you won't be the first author, but you may collect papers as second, third, etc, as well as see your ideas grow into a fruitful research.

Honestly, ideas are cheap. Most students and faculty have a dozen a week. Execution is expensive, and that's the part they are willing to do. I don't see a reason why you shouldn't help them.