I Became a Free Babysitter - Advice Please

Lurker gone anon because I'm going nuts about this and need advice. I would like to handle this delicately but it's starting to upset me.BG: My partner and I have two kids, they're 5 and 2. The 5 year old is in school and the 2 year old starts in the fall. This past year has been hard financially/personally, so we have no childcare or help around the house and we're in a tough "season of life" or what-have-you where we seem to always be trying to pick up after the kids/pets, squeeze in work, and manage some difficult medical things. We work from home but it's not an ideal or cushy situation.Our 5 year old has a friend at school whose parents have more children than we do (their other kids are older). When they realized we both worked from home, I think they got the impression that we just kind of loaf about and they started asking for "playdates" on a weekly basis with their kid -- usually at our house but sometimes at an outside activity where we're supervising. They never offer to reciprocate. This has been going on for about 6 months but it's gotten much more frequent. The time frame ranges from an hour or two to more like 6 hours. Once one of them made a comment at school drop-off asking if I was going back to bed. Nope, actually going home to apply for jobs while I simultaneously wrangle my toddler and try to fold laundry. It really stung. I left a FT job to care for my kids and try to support my partner, and every day of parenting + work stuff + therapist/doctor's appointments for a family member + general household business is more stressful than my job ever was. Adding another kid to the mix makes it infinitely harder -- they're not old enough or chill enough to play unsupervised at this point, plus we have the toddler in the mix who we have to keep separate from them.I don't want to ice this family out, because we all like their kid and our kids will continue to go to school together for a while. They're also pretty nice people but seem to have latched onto the idea that we welcome the opportunity to babysit for free. We turned down the last "playdate" because we had a conflict, but the parents keep asking and I want to let them know that we're not their unpaid childcare resource without insulting them completely. It's always phrased as "can x and y have a playdate at your house on [day]? we have [appointment/party/etc]" and it's making me crazy -- it always sounds like they're making arrangements with a babysitter. Most of the time when we have playdates with 5 yo's other friends, one of the parents of the other kid is present (so we can chat and split up supervision) or it's clearly a favor we're doing the other parents and we don't mind because it's framed that way and we know they'll cover for us if we need. This feels different, kind of disrespectful. What do you think? via /r/Parenting http://ift.tt/2t3kr2x