The K1 visa is for you and the K2 visa is for your kids, if your fiancé wants to file for a fiancé visa. When your fiancé starts filing the documents, make sure to do K1 and K2 at the same time. Otherwise your kids could get left behind.

Get married in the Philippines and have him petition for you and your kids as a foreign spouse. The fiancé visa is temporary, so you'll have to adjust your status again later. If you're not in a hurry, get married and go the spouse visa route

Make sure you have lots of photos documenting your relationship

https://www.visajourney.com/ Lots of good info there

Like someone else said here, the K1 fiancé visa. It's faster than the spouse visa. We've now been waiting 21 months for our K1 process to finish

If your kids are minors, there shouldn't be a problem.

There's a lot of wrong information here. Assuming your fiancé is a US citizen, the current processing time for the initial petition is twice as long for a spouse (25.5 months) as for a fiancé (13 months). The screenshots below are from https://egov.uscis.gov/processing-times. Even after the I-129F or I-130 is approved, you still wait about another six months for the interview. The K1 I-129F petition (https://www.uscis.gov/i-129f) can include your children, so you pay the $675 fee only once. In the US, each person has to file an I-485 separately to get a green card after the marriage. Those fees are $1,390 for ages 14 and up and $950 for under 14. The I-130 (https://www.uscis.gov/i-130) costs $675, but if the sponsor is a US citizen or plans to become one before your US visa is issued, three I-130s have to be filed and three fees paid. The only advantage of the spouse visa is that it comes with a green card at a lower cost, but it takes much longer.