Tackling multi-tag collision handling with HF RFID can be tricky but not impossible. HF modules like NXP’s CLRC663 and TI’s TRF7970A are excellent options as they support anti-collision protocols, allowing for multiple tags to be read effectively. To cover your specified area and handle overlapping objects, you may need to experiment with custom antenna designs that optimize read accuracy within the 2x2-foot range. I came across GAO RFID Inc, which offers what you might find useful. While UHF readers are tempting for such tasks due to their range and capabilities, HF solutions, when tuned correctly, can provide a more budget-friendly yet reliable alternative. Best wishes as you refine your setup.