General Visa Advice

Hello,

I am a British born citizen and have been in a relationship with my Gambian girlfriend for 2 years now, and am looking for advice on how it is best for us to proceed regarding living together permanently in the UK.

We met when I went to the Gambia on holiday 3 years ago, and became good friends and kept in touch throughout the year. When I went back there on holiday again the following year we grew closer and began our relationship. Since then we have kept in touch daily via Skype and Viber, and I have been back out to the Gambia 5 times over the course of the last year whenever time would allow. It's not easy being apart but we are very much committed and in love and are determined to make our relationship permanent no matter how long it may take.
She also has a 10 year old daughter, whose father has had nothing to do with her since she was born. In fact he has never met her as he wanted nothing to do with her and they do not even know where he is now.
We have decided that we all want to be together as a family, which leads me to my questions on the best way forward to us?

Ideally I would love them to be able to come and stay with me for a holiday in the first instance, to give them a taste of UK life and to meet my family. But from what I read it is nigh on impossible to get tourist visas and we would most likely be refused. So if we tried and failed would that look bad for future visa applications?

Another option may be a spouse visa, but we don't want to feel pressured into getting married, but maybe it's our only real hope of getting a visa?
If we did get married and then applied for the spouse visa, would her daughter automatically be allowed to come too?

I am in a lucky position of having a good job (50k pa) and a nice home for us to all live in, so I shouldn't fail on any of the new financial criteria.
My girlfriend and her daughter both speak good english and have no trouble holding conversations and understanding english. So they should be ok with any english tests.

On the subject of the english tests and life in the uk tests, at which stage do these tests have to be done? Before or after they would come to the UK?

I have so many questions but I better stop my ramble now!

Any advice people can give is much appreciated.

http://www.workpermit.com/uk/fiance.htm
Life in UK test is for those already in UK applying for ILR or British citizenship