There won't be a great direct route. Probably the safest method would be bus to DD and then either walk or bus to SSR. Recent posts on SSR bus service indicate that the DD busses pick-up at the Marketplace and then go to PI, TL and ultimately SSR. So, if you have to wait any amount of time at OKW for a DD bus, you could easily be facing an hour trip by bus, including the transfer at DD.
Another option here might be a bus to DD and then boat from DD to SSR.
Boat service direct from OKW may be an option. However, I saw a post recently indicating that the boats were filling-up at OKW, and then proceeding directly to DD without a stop at SSR. You could probably tell the captain where you are headed and make sure he stops at SSR on the way.
A call to the OKW front desk (or inquiry at check-in) might help you determine the best option. The pool will already be closed a couple of months by the time you arrive, so hopefully CMs will be used to answering the question by then.
With the group of children you mentioned, you might be better off just sticking to the pools that will remain open at OKW.