I have 2 questions:

1) If a person on a tourist visa gets married to the US citizen while in the US, will it make it more complicated to apply for the adjustment of status and get a conditional green card? Is it better to enter on a K-1 fiancee visa?

2) When a person is applying for green card through marriage along with his/her unmarried children under 21, do the children have to be physically present in the United States at the time of the application? If not, do they have to immigrate within, let's say, 6 months after their green card application is approved?