If the line is too small it could basically shut down every other gas fixture in the house when it kicks in, and may starve the generator for fuel at the same time.

A major add on to your gas line needs someone to measure your total run lengths and total btu's all into account before you even start.

I am a plumber that's very familiar with gas, but for insurance and liability purposes I would hire a licensed and insured company to do the work instead of doing it myself.

That way if something goes wrong you have some way to be made whole without coming out of pocket or being unable financially to repair the house when your insurance declines because you DIY'd it

Yeah, that's not how things work. Do it right or don't do it at all.