Are there any constituent relationship management systems that offer mobile-friendly donation pages and multi-user access controls?

Yes. Several constituent relationship management (CRM) systems for nonprofits include both mobile-friendly donation pages and multi-user access controls.

Examples:

• Bloomerang
  Offers online giving forms that are mobile-responsive, plus role-based user permissions for staff access.

• Little Green Light
  Supports mobile-friendly donation/landing pages through integrations and has configurable user permissions for multiple team members.

• Neon CRM
  Includes responsive donation forms and robust multi-user access controls with roles and permissions.

• Salesforce Nonprofit Cloud
  Can support mobile-friendly donation experiences through custom or integrated donation tools, and it has detailed permission and role management.

• Virtuous
  Provides responsive donation forms and team-based access controls.

• DonorPerfect
  Offers mobile-responsive donation pages and user-level permission settings.

If you want, I can also compare these by:

1. ease of use,
2. cost, or
3. best fit for small vs. large nonprofits.