Since you're marrying for love, why don't baby-momma and baby girl join you there?

 

1 - Getting married in Poland for foreigners is a long tedious process with a lot of documentation required both from here and from your home country so you should provide at least a couple of months i.e. you have to complete all the documents BEFORE you can get married.

2 - Thats rather a question concerning UK immigration. You will need to apply for EEA Family Permit which can take any length of time from being issued on the same day to several months. Besides, keep in mind that there is no guarantee that you will get one just because of your marriage to a Polish citizen.

3 - I don't think you can extend Visitor visa in country neither can you apply for temporary residence unless you get married before the expiry of your visitor visa but read point 1 above again. Try to get visitor visa for six months to be on the safe side.

Alternatively, you can get married in your home country and then move to Poland with your wife and child. That will be a lot easier - as far as I can tell.

Good luck