Additional extras for donations

We have a client who uses GiveWP and were asking if we could set up an optional extra on their donation form. For example, their “Sponsor a child” page offers 3 donation options:

$xx – Sponsorship for 1 Child
$xx – Sponsorship for 2 Children
$xx – Sponsorship for 3 Children

They wanted to allow people to select an optional extra that could include tuition for the sponsored child(ren) too, for a small extra amount.

The only way I could think to do it was just to give 6 donation options like so:

$xx – Sponsorship for 1 Child
$xx – Sponsorship for 2 Children
$xx – Sponsorship for 3 Children
$xx – Sponsorship + Tuition for 1 Child
$xx – Sponsorship + Tuition for 2 Children
$xx – Sponsorship + Tuition for 3 Children

It would be nice though if it could have just stayed as 3 main donation options with a checkbox or something to additionally add tuition as an extra on top.

That’s not something that is possible right now is it?

The page I need help with: [log in to see the link]