Don't add the second kid on the website and have individual conversations with the hotels, at least when very junior (obviously much easier when you have an Ambassador to do this for you). I currently have a 3yo and 1yo.... I often find when speaking with hotels their website is essentially tracking adults.

My route to find hotel rooms on the Marriott website for the family are as follows:

1. Search for 2 adults, sometimes I use 2 adult + 1 child 3yo (e.g. Japan seems to be only counting adults for rooms, US is more flexible)
2. I then look at rooms to have ones with 2 beds (typically 2 queens), and manually check the rate details to see if a crib/cot is allowed (some smaller rooms, or the cheapest options may allow zero cots as the room just seem too small (never mind for 2 kids)
3. So if I basically see 2 beds in the room, and 1 crib allowed that is good. I then let my ambassador let the hotel know in advance. I ignore the "max people" at this point
4. There is a step 3, if I am booking a suite it normally has a king sized bed, and then I get my ambassador to see if they are ok with 2 "extras", i.e. roll-away bed/sofa bed + crib, before I book (or after booking if there is a flexible policy), they normally are since there will be enough space in the two rooms

Many hotels don't allow two cribs/roll-away beds (at least formally), luckily my 3yo is fine in a proper bed. I have had very few problems otherwise in fitting us all in, we look forward to rooms with balconies so that we don't have to hide in the bathroom whilst they sleep. Or spending more on suites.

(My kids are too small for a connecting room, which will come later on, and I am aware can be a bit hit or miss I understand - Hilton does it better I hear, but I'm not Lifetime status there!)