Coordinated beamforming across distributed base stations (BSs) in cell-free wireless infrastructure can efficiently support integrated sensing and communication (ISAC) users by enhancing resource sharing and suppressing interference in the spatial domain. However, intensive coordination among distributed BSs within the ISAC-enabled network poses risks of generating substantial interference to other coexisting networks sharing the same spectrum, while also incurring elevated costs from energy consumption and signaling exchange. To address these challenges, this paper develops an interference-suppressed and cost-efficient cell-free ISAC network, which opportunistically and cooperatively orchestrates distributed radio resources to accommodate the competing demands of sensing and communication (S\&C) services. Specifically, we conceive a radiation footprint control mechanism that autonomously suppresses interference across the entire signal propagation space to safeguard other networks without exchanging channel knowledge signaling. Then, we propose joint BS activation and beamforming coordination to dynamically activate appropriate BSs and orchestrate their spatial beams for service provisioning. Building upon this framework, we formulate a cost-efficient utility maximization problem that considers individual S\&C demands and location-dependent radiation footprint constraints. Since this results in a non-convex optimization problem, we develop a monotonic optimization embedded branch-and-bound (MO-BRB) algorithm to find the optimal solution. Additionally, we apply a low-complexity iterative method to obtain near-optimal solutions. Finally, simulation results validate the effectiveness of the proposed algorithms.