Il've made such requests when we booked the room through my HK travel agent, who had sent these requests to the hotel and stated our hotel voucher. We reliterated our requests when we checked in at the hotel reception counter.
I've also stayed at Swissotel the Stamford in early Aug. You can e-mail the hotel directly on your request. Last time, I e-mail the hotel and request for non-smoking, higher floor and twins bed room as I also have 2 adults and 2 kids. I agree with FiMaMa, the service of the hotel and the breakfast is very good.
We (2 adults & 2 kids aged below 7) stayed at Swissotel the Stamford in late Jul 2011. Free breakfast and 1 extra bed are provided. Although the hotel is a little bit old, the service is very good and their breakfast (choices of 2 restaurants) are good too, compared with those of Hardrock at Santosa.
We booked the rooms through travel agent in HK. The number of guests staying at the room was given to the hotel at the time of booking. Thus, I don't know the free extra bed was arranged due to this. I had experience that some hotels (eg Naurmi) has explicitly requested us to book 2 bedrooms suite, rather than 1 double room as they does not provide extra bed.
For Swissotel the Stamford, remember to request for high floor rooms, as the views are significantly different and the rooms are much decent.
Beware there's some hotels only accepting 2 adults +1 kid, e.g. Swissotel Merchant Court. Last time they advised me to book 2 rooms. So do send email to the hotels that you wanna book first before you pay, otherwise, either the bed size is not big enough, or they simply couldn't allow 4 ppl. For Shangrila Rasa, they allowed 2 children for free (12 years below). Some other hotels apply children age to stay free differently. So do check, don't assume it's free for 12 years below.