If you're still taking requests, could you do: "Ku kentaurit o puoliks ihmisii ja puoliks hevosii ni oisko se sit eläimiinsekaantumista jos panis kentaurii?" (I understand if this is too long, you don't need to do this if you don't want to! As tengwar probably doesn't have letters for ä and ö you can just replace ä with a although that'll change the pronouncication. But no one's gonna notice. Also I understand if you don't feel confident doing things in foreign languages.)
Ooh, I love a challenge! And no, Tengwar does not have symbols for these, but being a phonetic alphabet, I have a bit of wiggle room. Transcribing in Tengwar is based on sounds rather than specific letters, so I can use different symbols to try and convey the correct pronunciation.