Client acceptsSigns, pays if required. Becomes a client.
Activation runsAutomatically, on acceptance.
EngagementsOne per service that spawns work.
BillingDraft invoices and a running schedule.
You are not in the middle of this. Activation fires as part of acceptance, so the shape of what gets created was decided earlier — in the services and packages on the proposal. Review the proposal before you send it, because after that the work spawns without another look from anyone.