Hi Jan,
I've not yet done any DNA testing, because I have not had any need to do so. Now things may be different. As you probably know, the process is very simple - you swab the inside of your cheek and send it off!
But is it worth it in this case? Since your husband is a descendant of Ellen, we have to ask if Henry Thomas Butler was her father, or not. We are missing her birth certificate, and without it we have no information on her father, other than her marriage certificate, which is of questionable accuracy. If she was really born in Liverpool, I don't think HT could have been her father, as I have no information showing an association with Liverpool before 1875. But I note that in the 1891 census, Ellen (now Hunt) records her birthplace as Kennington.
I DO think that HT was the father of Henry William - everything seems to match up, and lacking any other Henry Thomas Butler actors at the time in London, the evidence seems compelling.
I suspect HT was not the father of Charles Edward, simply because in late 1871 HT and his family left London and were never based there again. Having said that, I don't know where HT was in June 1879, when Charles would have been conceived. He had been performing in South Shields the previous month, and from mid-1880 was based in Hull, but in between I have found no trace of him.
So, my question to you ... have you traced any living descendants of Henry William? They would be the best bet for proving that HT was the father. But basically, if descendants of all the three children were to take DNA tests, together with myself, it would show (or disprove) common parentage.
Regarding Henry Thomas Butler, my frustrations with tracking him down can be found at this thread:
http://www.rootschat.com/forum/index.php?topic=318087.36 I will also send you a personal message with a biography of him.
Cheers
Tim