Why not just wait until you have the main tank up and running? That way you will save some money as well as not putting the fish through more moving than they should go through.
To answer your question though, a 29 or 30 gallon would be good. Don't go with anything smaller, you'll have more hassles with a 10 gallon versus a 30 gallon most likely. A 10 gallon is not reccomended period for angels, even at a small size, unless they are just small fry a few weeks old, which I'm sure you're not getting LoL
IMHO I would strongly suggest that you just wait until you have the big tank you're planning on getting and then add the angels once it's cycled, but that's just me
Good luck to you and enjoy your angels when you get them! :clap: They're great fish! I love mine!