Investing now for retirement is a good idea--it has so much time to grow! So, definitely consider that. Since you're so young, I would also plan for the possibility of home ownership and children down the line. You may do neither--certainly, it doesn't sound like your short-term plans include either, but both would take a lot of $$. So, investing for retirement right now makes sense, as does having more in savings. Once you've settled down (after your South Africa adventure), home ownership might look more appealing to you. Children might, too--emphasis on MIGHT.
Sorry about your mom. The only thing I would suggest there is, you know your mom, and you know what she'd like for you to use that money for. Emergency savings, living it up a little, education for potential future grandchildren, whatever. And in your mind, maybe earmark it for future expenditures that would make your mom happy. When my mom died, I got a small inheritance (~20k), and spent a lot of time thinking about how she would want the money directed. For me, it was family time. For you, it might be something completely different.