Pat. Nice to meet you. And I love the vision of delosperma and sempervivum growing around that lovely mailbox pillar.
Delosperma, even the cooperi is easy to control since it has such shallow roots. Just pull/dig it from where you don't want it to go. These pieces will start easily any where else you may want it to grow.
I agree with with the other suggestions here, give it good draining soil and an area that does not sit in water at times of the year. That would be lethal to both the semps and delosperma.
Would love to see photos of your semps. What a great memory story behind them.