No, not over cautious at all, it's a wise move at this time of year. Any young plant seedling is tender and, if nipped by even a light frost, it will turn their tender leaves black and shrivel them. That can set them back a couple of weeks, so best to avoid it if you have a greenhouse or potting shed to move them to. Or, if the pots get a bit too heavy to start lugging in and out at night, you can just cover them over with horticultural fleece or an old bit of net curtain works just as well, (but maybe I shouldn't mention that!
) and that gives frost protection too. By the end of this month the risk of frost should fingers crossed be over. ?