Hi, I dont think you have to worry about what to bring in Doha. relatively, you'll find it interesting to see most of the things you have from your own country in here. Supermarkets vary sometimes on products, but in most cases you'll find what you are looking for in one supermarket to another.

Tacos, check.
Vanilla, check
Marshmallows, check.
Splenda, I dont know what that is...but, check (it could be in the Base)
Crystal Lite, check.
Spices, check (they have the FULL range here!)

See yah!