AWESOME user name! Have you considered doing a partial plan in the 300s? That's what we have right now and it's a good deal given how many games we go to.
I was going to suggest the partial plan as well, plenty of good seats in and around sections 205 and 225. If they want to attend 9-10 games, pick a 20 game plan and StubHub the extras. Finding a full season group would probably be a bit cheaper, but the added flexibility of picking games and the STH perks would make it worth the slight extra cost.