Hello. You could setup a custom field for age, where based on the selection of the user, the cost is modified. So $50 could be the base cost, then if they choose Option 2 they get a $10 discount, if they choose Option3 they get a $50 discount. So that part is covered.
Then for group registrations, you could apply that age field to each member in the group so they are charged accordingly. For group registrations you can not currently set a maximum $ amount for the group, but you CAN set a maximum number of people. So, you could say not more than 10 people can register in a group, but you would have a fee per person in the group still.