As long as you are going with the default option of keeping orders open, your staff will be able to see & close those online orders.
If they cannot see them under your open checks screen, you will need to review the Employee Class permissions for those employees as their permissions may be limited to only see their own open checks vs all open checks.
If you prefer, you can also request that all online orders pass through to your POS using an employee ID code that all your staff use ie. Manager / Counter / Server