Ismaning might be quite nice but I doubt it's really that much different from
Unterschleissheim.
Plus it's on the wrong airport line to get to Haimhausen. You need to be on the S1 for Haimhausen, it's just a short bus ride away from Lohhof S-Bahn. If you went for Ismaning you'd have to go out to Besucherpark and then change onto the S1 to come back up to Lohhof, right?
I've never lived around Unterschleissheim, but I've worked around there for the last 8 years, know the area quite well, and know plenty of families that live there. Personally I would go for Unterschleissheim or
Oberschleissheim.
It's not a pain in the arse to get into the city from there - it takes exactly the same time to get from Oberschleissheim to
Marienplatz on the S1 as it does from Ismaning on the S8, and the trains are just as frequent. Plus you have the option of changing at
Feldmoching onto the U2 for fast access into Schwabing. I take the S-bahn from the city out there every day, and it's just fine.
Neither Unter- nor Oberschleissheim are particularly the center of the party universe, either, tbh, but there are plenty of parks and things to do (a branch of the
Deutsches Museum is out at Oberschleissheim), and there are Kindergärten etc as well.
Or you could take up the suggestion to go to Freising, but then you really do have a major trek (45 minutes on the train) when you want to go into Munich.
Eching and Neufahrn - whenever I have the misfortune to have to go there I feel like falling asleep. Yawnsville, both of them. Sure, parks and stuff for the kids, but you yourself would probably go nuts with boredom. I would, anyway.