Congrats on the holding females. I am going to go against setting up the 10g tank and say go for the 29g tank for the fry. There is an awful lot of hiding places in the tank and as it is their first brood, they may not hold to full term anyway or actually eat the eggs.
If you want to remove them, then put them in the 29g tank. The females will NOT eat at all, while they holding but once the fry are born, remove the females as soon as possible. The females can be in the 29g with the fry for a few days until they get their strength back and are eating.
It can be quite a challenge having two females holding at the same time, and when I had fish holding in my 180g tank, I left them in the main tank. The more hiding places the better for the young ones. Fry are very good at hiding provided there is enough places for them to hide, which your tank has.
Keep us posted as to how things develop, fry should be born in 20-25 days or there about but please DO NOT be discouraged that they dont hold full term or eat the eggs, it can take a few tries for them to get it right.