I wouldn't go for the ds option if you're gunna go with an original ds. Original ds is clunky, ugly, has very dim brightness, and is a pain to hold. The ds lite still has a GBA port and it's so much sleeker and has a normal brightness. Though if you're gunna get the GBA sp 101 make 100% sure it's a 101 and not a 001. It's hard to tell for me a lot of the time because the only place in my area you can get them are cons and almost all the gameboys sold are both dead and the labels ripped off so there's only one other way to check. This also applies online when the pictures may not show you the label.

These are my two advance sp. The dark blue one on the left is a 001, you can tell because it has the typical gray gameboy screen, it has a crapass frontlight screen. The steel blue one on the right is a 101 and has a black screen like you see on all backlight electronics today.
I hope this helps, I ordered the dark blue one online which made it hard to know it wasn't a 101. If you order it online look for pics of the gameboy open with the screen showing so you can know if you're actually getting the 101
edit: I forgot to mention!! Personally, I wouldn't go for the emulator option especially if you're using an iphone. The free ones are usually laggy and crash damn near every time you go on multi-tasking. Half the time I try to restore my last save it ends up crashing/playing for a few seconds then freezing too. Suuuper frustrating.