Believe me I know the feeling of guilt. I did the same when Leroy passed. But I believe and always have that the day we pass over is all ready set, even for animals. It doesn't matter if they go on their own or are 'helped over', it is their day to go home. I mentioned to God last night and again this morning that a very special hammie named Olivia, would be coming home to Him soon and please send a very special angel to help her over. Of course He all ready knew she was coming and I'm sure she was greeted with many cuddles and kisses. She's probably helping decorate the Rainbow Bridge for Christmas right now.
Prayers are with you and Helen. I know how hard it is to let them go but the love always remains.