Raja Ampat is a good choice, but be aware that in April, many/most of the liveaboard boats will be making their way back to the Komodo region. So some of the April trips are going to be between R4 and Ambon, around Ambon, or between Ambon and Komodo.
In truth, from Bali it's not just a hop and a skip to reach Raja Ampat. If you don't want to leave Indonesia and pay for another visa to get back in, you need to fly to Makassar/Ujung Padang first, and because of the early morning departure times from UP to Sorong, you need to overnight there. You can also get to R4 through Manado via Singapore, but it's a similar problem--it usually requires an overnight in Singapore or Manado, and it requires you to leave Indonesia and re-enter. A third option is to go through Jakarta, and you can get there in a single day with aircraft changes in Jakarta and Makassar. It's quite a trek!
In truth, from Bali it's not just a hop and a skip to reach Raja Ampat. If you don't want to leave Indonesia and pay for another visa to get back in, you need to fly to Makassar/Ujung Padang first, and because of the early morning departure times from UP to Sorong, you need to overnight there. You can also get to R4 through Manado via Singapore, but it's a similar problem--it usually requires an overnight in Singapore or Manado, and it requires you to leave Indonesia and re-enter. A third option is to go through Jakarta, and you can get there in a single day with aircraft changes in Jakarta and Makassar. It's quite a trek!