Maths: Singapore or MEP, perhaps moving to AOPS later.
In general, look for opportunities to go wider or deeper rather than just steaming ahead. Not just textbooks either, puzzles, mystery/detective books, strategy board games, learning to program...
Also, have you had your older daughter tested to see if she is 2e? If everyone else in the family is gifted, it's very likely that she is too, but its hidden by her learning challenges.