Originally Posted by
Happy
Not going to happen in most European city hotels.
Often you need to book a 2 persons first and then email the hotel to check if they can accommodate you by switching to upgraded room and then charge extra in cash. You can forget about "no additional charge" part if your destinations are in Europe. The hotel if it can accommodate would tell you how much is the charge and you would pay that directly to the hotel upon check in or check out. The 7 night cert is just for standard room which in Europe often is strictly 2 guests only.
I have had pretty good luck in London over the years. Look for hotels that have rooms with two double beds or a double bed and a sofa sleeper. Call or email the hotel and let them know you will be bringing a child and need to find out if their rooms can accommodate the child without a rollaway. Lots of the London hotels charge crazy prices (like £50 per night!) for a rollaway bed (in addition to any extra person charges!). Ask to confirm that there is no charge for a third person if they are a child.
Many of your best London options are dropping lower in the new program. The Regents Park, West India Quay, and Maida Vale Marriotts will all be Cat 5. I've checked these and they currently charge a supplement for the third body on a Rewards booking, but in my experience if you book for two people and email to ask about the child, you have a good chance of avoiding the charge. The Moxy hotels will be Cat 4, but they are more distant from most tourist spots.