when mum did FDC, if there were adults that were regularly in the house, they had to notify the council she was employed by and that person had a police check to confirm they were ok to be there. but being a home environment, people will sometimes just drop by - it would be rude to stop them coming in i guess.... i really depends on what access they have to the children - if he was in the kitchen and not in direct contact with the children....

she's told you she has older children, perhaps it was her son or something. i dunno. if you are uncomfy, mention it to her - that you just want to make sure you know what other adults are going to be in the house when your son is there....