Should I suggest my sources as reviewers?
The fact that you cite their work, and that you use their work to inform your work, does not present a conflict of interest, and it's fine to suggest them as reviewers. Doing so might even be a good idea, since they might be naturally qualified to assess your work.

An exception might apply if your work stands in some way in direct competition to their work -- for example, if you developed a technique for addressing the same problem, and you claim that your technique works better than theirs. I've seen a few listings of conflict-of-interest criteria that include a conflict type "competitor", and other listings that don't. If this applies, I would recommend to look for the conflict-of-interest criteria of the target journal/conference. If you can't find anything, you might want to contact the editors/chairs.