Hi guys. If I was accompanying a band on the piano in jazzy blues tunes such as Now's The Time by Charlie Parker and Cedar's Blues by Cedar Walton (12 bar progressions) should I add 9ths/11ths/13ths to 7th chords?

Thanks

Yes. Skip the 11th unless you raise it a halfstep. Here's nice voicing for major 7th chords, bottom to top F7: Eb A D G C F, stacked 4ths.

Thanks.

In most jazz blues, after you play the head, a typical chord sequence for soloing would be:
I IV I I
IV IV I VI
II V I/VI II/V

Klonk - do you mean dominant 7th chords instead of major 7th (your F7 example doesn't correspond..)

Yes.