Hulashaker, what a lovely thing you are doing, so sorry about your mum 
I use a woven wrap sling, they are more cumbersome but I'm very fast at tying one now (lots of practice!) and for DS's size and weight (he's very tall and wears age 6-7 years clothing) they're the most comfortable.
I like Kokadi ones best, but also have a one from Little Frog in Poland, excellent quality, great prices and a great range of colours. They ship worldwide and have a great website, I actually got a seconds quakity one from them and apart from the design being a bit more wavy its perfect. I go for the cotton ones as more supportive with older children.
A friend of mine still gets away with a Stoke MyCarrier for her three year old, you can often get them cheap second hand from eBay and the few time sive carried her daughter its been pretty comfortable and very fast and easy to get on and off. There are more men tai style ones (think Tula do one?) But woven wraps have always worked best for us so I don't much about other I'm afraid. Do you have a sling library near you where you could try some out, and borrow one? Also, another friend in the UK always borrows one for her holidays from a website called something like "its a sling thing" its an online sling library.
One last point, I have carried DS in a sling since he was born, so my stamina and endurance increased as his weight increased, carrying a child if you haven't before takes a bit of getting of used to, so practice for a couple of weeks beforehand if you can. I use a woven wrap as Its the only type of carrier I can comfortably carry him in now he's much bigger, so long as you tie it correctly it spreads the weight fantastically and doesn't strain you. I am not very strong and not in the best of health but I can carry DS for several hours nmon stop without getting too tired.
Hope that helps!