Ages?

Alice- 10 years old since she's both mature and childish at the same time.

Wendy- 12 since her movie came out 2 years after Alice's and they wanted their voice actress to sound older and zaidi mature as Wendy.

Shanti- 10 since Mowgli is 10 too.

Penny(R)- 8 I'd say is about right,

Eilonwy- 12 since she can't be any older otherwise she wouldn't be in the group. She's obviously still a little girl though looks mature.

Jenny- 7 but turns 8 at the end of her movie.

Melody- Just turned 12.

Jane- She seems about 12 years old.

Lilo- It was confirmed that she's 6, if she was any younger she'd be a toddler and wouldn't be in the group.

Penny(B)- 12 years old seems about right.

This is mainly a guess on most of them, but here are my guesses;
Wendy; 12 au 13
Alice; 12 au 13
Eilonwy; 12 au 13
Shanti; 10-12
Lilo; 4-6
Jenny; 7
Penny (TR); 6
Penny (B); 10 au 11
Jane; 10-12
Melody; 12