Mattress choice for a 3 year old

Hi. I have to begin by commending you on your excellent website. It is a great source of information and I have learnt so much. I still require your help however.
I am looking to purchase the first bed for my little 3 year old who currently sleeps in a cot. I am aiming to go for a small single due to restrictions of the room dimensions.
Your 2 drawer format is illustrated as 1 drawer per side. Is this still the case for the small single as you state that drawer depth is 20” but the total depth or width of the small single base is 30”? Can you please clarify whether for the small single base, the drawer format is still one drawer per side but with a reduced drawer depth or whether the drawers are still 20” deep but with the format as 2 drawers on one side? I am hoping that it is the latter as one side of the bed will be against the wall.
I am hoping to go for an origins base as I don’t believe the extra support of the base is necessary due to my 3 year old child being light weight; the mattress doesn't have much work to do anyway. Is this a wise choice?
Regarding mattress options for 3 year olds, and taking into consideration that the mattress will have to be suitable for a number of years and that it may be used occasionally by adults, what kind of mattress would you recommend? I notice that your pocket sprung mattresses don't come in small single, is that correct? I am however interested in 100% Natural Latex in the form of the fusion 5... I like the fact that the mattress is relatively shallow, I want my child to find it easy to get in and out of bed and coupled to the origins divan would give a total height of 48cm or 53cm with castors fitted. Would the fusion 5 be a good choice for my child? Would a latex topper offer any benefit or would it be unnecessary? Thinking out of the box a bit, would a latex topper alone, say 5cm or 7.5cm be sufficient for a small child? Even if it were suitable, offering adequate support, I can however see problems with obtaining bedding to fit.
I have read that you recommend not using slatted bases with mattresses as the fillings have potential to sag through the gaps over time, and ultimately reduces the life of the mattress, is this correct? My next question is regarding the use of bed guards, many of which fit under the mattress. Is this likely to affect the performance of the mattress and reduce the life of the mattress?
Thank you in advance for your help and guidance.