@karmomof3 - I am quoting myself above just in case you missed the response to your first couple of posts. I changed them to the same color so you know what response goes to what post. Helps me keep it straight in my head too. I know this thread moves fast. You got tons of people who here are amazingly knowledgeable on Southwest Companion pass and booking on property Disney stays with UR points. That is not my area of experience. So, I'm going to focus on helping you with guidance on International destinations which is more my speed. I did a quick search to see who flies out of GRR to LHR and it is mostly AA with connections in ORD. There was a smattering of Delta and there are some United flights as well. Since you mention you like to go for the cheapest flights and won't use Spirit, are in 1 player mode for the credit cards applications and have 4 people traveling, I am going to make the assumption that your goal is to get yourself and the kiddos to London with the fewest points possible and the least out of pocket possible.
I am going to suggest that you completely avoid using British Airways as a transfer partner for UR points. The program is distance based and the taxes and fees for flying to or connecting in London are simply outrageous. BA is only worth it for easy first class awards at nearly the price of an economy ticket in taxes and a bunch of points. I think you could actually do well by utilizing United as your airline for London. United is a 1:1 transfer partner for Chase Ultimate rewards. I chose some random dates (July 10 with July 17 return) and saw that you could get 4 people on a RT saver economy flight from GRR-LHR for a total of 240,000 United miles and $806.44 in taxes. If you have the CSR you could use your annual $300 per year travel credit to bring that $806 down to $506. The same exact flights cost $4,490 total. If you chose to pay for them with UR points in your CSR account you would need 299,334 UR points since they are worth .015. You would not be paying out of pocket and you'd earn UA frequent flier miles. The difference in UR points cost is 59,334 which has the value of $890. Given the exact same scenario, this is where I'd pay the entire thing through the UR portal with UR points and earn the butt in seat miles. Sometimes though, you will find more value in transferring points from UR to UA. I'd be sure to always make a comparison before leaping one way or the other. Those same dates had other airlines available for similar pricing. So this gives you the general idea that depending on when you travel to London and when you choose to book your travel you are going to want to plan to have about 300,000 Ultimate rewards points to use. FYI Delta would require 320,000 Sky Pesos, $800~ and had 2 connections as opposed to 1 with UA. You could use Korean as a partner t book Delta but you'd still be stuck with the 2 connections sine that is what would be available to a partner airline.
In your shoes, my plan A would be to earn all the UR points I can and pay for travel through the UR portal. Plan B would be transferring UR to UA to book flights and leverage the CSR to mitigate the taxes and fees. Plan B would involve also picking up the United card at some point, just not before you have all of the UR earning cards. The reason would be to have the ability to see awards only available to card holders and also to be able to get an additional 25% bonus when using the United Mileage X app although I would not use that card for the purchases. I'd also join the United Mileage Plus dining rewards network to pick up extra points. In addition, I would use the Chase UR shopping portal. As for the UR earning cards, I would suggest you get the ones with the highest bonus offers and I'd suggest you double dip the CSR and CSP first. I'd keep the CSR and at a year PC the CSP to a Freedom. Also, get the CIP for the bonus and then PC to the CIC as this one will be a very strong earning card. This is just for your London plans. It seems like you also need to work in 2 applications at the right time for the SW CP.