Well worth a try just with seals. You might need pistons you might not. Pump the lever until the pistons are part way out – hold one in if it moves easier than the other. Then strip the calliper. You will probably find dried on muck around the pistons which stop them going all the way in – or it could be as simple as too much fluid ( if the reservoir has been topped up with half worn pads this is possible)
Clean the pistons up – rebuild with new seals. I am a big fan of using red rubber grease to lube pistons – its better than using brake fluid.
YOU might even find that pumping the pistons part way out, cleaning and lubing them then working them in and out a few times is enough to restore them to full working order. Its always worth a bleed thru to replace the fluid as well