儿 is used as a separate word in all these words. It has nothing to do with "son, child" here (and in most other cases). It just makes something more like a nickname (like Bill->Billy in English).名词昵称通常会在后边加个儿字，像马儿、猫儿、狗儿等，人名则有青儿、蓉儿、过儿、靖儿等。儿字怎么念？是像“玩儿”那样和前面的音连在一起，还是想“儿歌”那样独立成音？
baosheng said:I'm pretty sure that the "儿" has to be attached to the previous syllable when it comes to the end of a name, but I'll let the "natives" confirm!
But you should write it out in expressions like 哪儿、这儿、那儿、一会儿。Personally I also suggest not to write 儿化音s out at all, otherwise there would be too many 儿s and difficult to read.