Well, if your letter is full of love then do it, but if it's not then don't send it, Make them feel your love in this hard time, Maybe a vist with some nice flowers would get your message to them better.
I believe argument wasn't in the mind of the Samaritan when he saved the poor Israelite man
10:30 Jesus answered, “A certain man was going down from Jerusalem to Jericho, and he fell among robbers, who both stripped him and beat him, and departed, leaving him half dead.<SCRIPT type=text/javascript>cj(10,31);</SCRIPT> 10:31 By chance a certain priest was going down that way. When he saw him, he passed by on the other side.<SCRIPT type=text/javascript>cj(10,32);</SCRIPT> 10:32 In the same way a Levite also, when he came to the place, and saw him, passed by on the other side.<SCRIPT type=text/javascript>cj(10,33);</SCRIPT> 10:33 But a certain Samaritan, as he traveled, came where he was. When he saw him, he was moved with compassion,<SCRIPT type=text/javascript>cj(10,34);</SCRIPT> 10:34 came to him, and bound up his wounds, pouring on oil and wine. He set him on his own animal, and brought him to an inn, and took care of him.<SCRIPT type=text/javascript>cj(10,35);</SCRIPT> 10:35 On the next day, when he departed, he took out two denarii, and gave them to the host, and said to him, ‘Take care of him. Whatever you spend beyond that, I will repay you when I return.’<SCRIPT type=text/javascript>cj(10,36);</SCRIPT> 10:36 Now which of these three do you think seemed to be a neighbor to him who fell among the robbers?”
<SCRIPT type=text/javascript>cb(10,37);</SCRIPT>10:37 He said, “He who showed mercy on him.” Then Jesus said to him, “Go and do likewise.”
But of course the decision is all yours and if you think a salvation letter will show your love then do it, but personally I wouldn't do that.