Almost all pianists think they have small hands
But though you cannot manage more than an octave you can probably also, with practice, do that with the fourth or even third finger also.
Should you stick to the white keys to make things easier?
I think we can prove that playing in keys with lots of sharps and flats is easier and produces cleaner results. Even putting little octave runs into your tunes may actually produce better results and reduce problems of clipping the wrong note.
This video Below shows you how to get your "small hands" going playng in octaves
You may not have such a problem as you think.
Even if you can only juat atretch an octave, by organisation and maximum use of all your fingers you can probably make such a big sound no-one will eveer suspect.
First look at this video froma person who used to think he suffered from this problem then we will go on to discuss his solutions.
Yes mine!
Video below of Too Beautiful To Last a Big Sounding Piano Performance
See and hear playing in tenths with your left hand and how to do it below
The distance between your little finger and thumb is not the only way you can utilitse the maximum stretch between your hands.
Because This is not the only aspect of what you can do for this problem
The conventional way of playing octaves is just to use 1 and 5 with wrist movement
1/ - Lack of mobility, takes away the connection between the melody notes if you are trying to phrase them
2/ - Instability because you are dexcending from space and may hit any point, particularly if moving more than one next door note.
Either change this sytem or
Add extra notes!
CHANGE - By using 4th or even 3rd finger after the 5th if you are able, when moving to adjoining notes
ADD EXTRA NOTES - an extra note played in the middle of the octave notes which the octave can pivot around for stability - either held down between both notes or played again with the new note.
This is likely to be roughly in the middle a fourth or fifth from the top note, but may also be a third from the top
Extra notes Makes it an Even Fuller and more impressive Sound
However, do make sure that this is a natural gradual process, do not force it
When doing large stretches make sure they do not feel too uncomfortable
It is better that they are not "held" so strongly, and they can be more relaxed when you use the sustain pedal for support
With practice you will find your stretches not so stressful after all as your hands will gradually adjust.