I'm so sorry for your loss - and please don't worry about your holiday in Arillas, it will be lovely. Are you going through Thomson or have you booked independently? - and how many of you are in your party/each room? We have stayed at Kaloudis 3 times and never found the music to be an issue. Yes, it's on and stays on until gone midnight but it's not thumping dance/house music or so loud you can't sleep. The first 2 years we went through Thomson and were in Roula's studios (near the shop, with bedrooms facing the beach, away from the music) and this year we rented one of Roula's apartments - which are VERY peaceful. Billy's apartments are right next to the bar.
If going through Thomson and there are 2 of you, give Thomson customer services a call and request a high floor studio. That way you are guaranteed to be in Roula's studios which are set back from the pool/bar and the music will cause minimal distruption. If there are more in your party there is one larger apartment on the ground floor in the block where Roula's private rentals are so you could request that.
If you've booked direct with Billy, then you can email him and see what he can do, but his rooms are nearer the bar anyway. If you've booked direct with Roula then her private rental apartments are very quiet. Either way, you'll be fine - everyone there is so lovely that you will find yourself relaxing and having a great holiday.