I apologize for my error, I searched the Marriott website for Munich and for Germany hotels last night and found no Munich hotels, yet you are right, today they are there.

Priceline is a good option. But you do still have time to earn hotel points. However, there are lots of differing opinions on what type of hotel to stay in. I usually try to stretch my hotel points to get the most free nights possible, but have often regretted not staying closer to the center of the city. It is so nice to be able to return to your room in the middle of the day to relax for an hour, without having to trek a long ways to get there. Location is a big factor in deciding where to stay, and ultimately, only you can decide which hotels would meet your criteria.

I recommend you research hotels for Mariott, Hilton, and SPG in both London and Munich, pick the one hotel you would prefer to stay at for each chain in each city, and write down how many points it would cost. Decide which city is best to use your Marriott points. Then consider what it would take to meet the goal points in the other city with another hotel chain. For Hilton, consider the VIP award charts (this one or this one) since the Amex and Citi Hilton credit cards will give you silver or gold status, allowing you to use them. The Hilton Amex also lets you redeem discounted 4 night stays, called AXON awards.

There are lots of cards to earn Hilton points with, from Amex, Citi, and Bank of America/Bank of Hawaii (because Hawaiin miles and Virgin miles transfer to Hilton 1:2, 5,000 miles = 10,000 points). With SPG, you can earn them from the SPG Amex personal, SPG Amex business, and your partner can apply for the same. I did refer my spouse for the SPG Amex a couple months ago, and the 5,000 point referral bonus posted several days after his application. Rumor is that the SPG Amex bonus will go up to 30,000 points in a couple weeks. SPG cash + points redemptions are a great value when you can find them.

Priority Club and Hyatt are also good for European hotels, but they require a Chase application. I have found that Chase will approve us for a new card about every 95 days without having to talk to the reconsideration line (not always instant, but the card comes in the mail within 10 days). I do periodically close a card or two, even though the common advice here is to wait until you open a new account so you have something to negotiate with to open the new account. Other people have succeeded in opening more accounts in a short period of time, but this is what has worked for me without needing to call.