Don't worry about bloom times or the possibility of pollination. Polinated daylilies form a seed pod. After your daylilies bloom just snap off any pods that might have formed. If the entire scape is done with no more buds just cut the entire scape off. But they don't always form pods.

And even if they do form pods and go to seed, it's pretty unlikely that the seeds will turn into full-sized plants unless you want them to.

It's relatively easy to hybridize daylilies on purpose, but it's also easy to avoid hybridizing them by accident.

Nate

Wonderful! I really wanted to group my daylilies together but was worried about losing diversity... I'm not scared anymore! Thanks for the advice :)
- Rachel