DH and I have 3 couple friends (well my brother/his DW, her brother/his DW and another couple). We all live pretty close to each other, have kids of similar ages and get along well. Of the group, 6 of them are keen fell/trail runners, DH is one of them, I am not and actually hate it. Since mid-last year it's become a bit of thing where the 6 who like running go out on a Sunday afternoon 1/2 times a month and myself and the other friend who doesn't like running stay back with all the kids. There are 9 kids total (7, 7, 7, 5, 5, 5, 4, 3, 3), my brother has a massive house with a large playroom and a sunroom which the kids can run around in, plus massive gardens with tennis court/tree house etc, so we all gather here, even though both brother and his wife go running. Me and my friend are then left with all the kids for anything between 3 and 6 hours (counting for driving to start point, run time and drive back, plus conditions in the winter are slowing them down, especially when they go for the fell running option and end up on icy, windy ridges). When they get back we take all the kids to the pub for dinner, but this can be as late as 6pm on a Sunday!
For a while I didn't mind it, the kids get on well and sort of split into groups and entertain each other, but it is hardly stress free. It has got to the point where I somewhat resent it, the other mum I am with doesn't seem to mind as much and I am happy to do it sometimes, maybe once a month and I'd do it every fortnight if i was at home with my kids while DH was out but being in someone else's house with 9 kids makes it very intense.
I'm often tempted to say I can't do it anymore but i'd feel awful leaving the other mum with 7 kids to look after alone and since they started going together as a group DH has seen a massive improvement in both his health and mental health (he used to get quite depressed), so I don't want to stop him doing this and he does take the kids out on other weekends and the other friends do help us with childcare often.
AIBU to resent this? Should I bring it up or keep going since they do us favours and this is DHs only real hobby?