My son (12, so he can move on his own) and I will be going to Poland and London from San Francisco this summer, so I'm wondering about connection times and potential checked baggage issues.

Flight out seems straightforward, SFO-FRA-WRO (Wroclaw). We can go for either 1h40m or 2h40m layover at FRA. Since it would be the same booking and all *A, would we need to deal w/ checked bags at FRA or not until WRO? (I'm assuming it's something like passport control & cary-ons at FRA, checked bags at WRO, but I really have no idea.)

WRO-LHR is more interesting. Options include via MUC with layovers of 1h25m, 1h45m or 5h5m or DUS with 1h25m or 4h10m. (There are flights through FRA, but they're roughly twice the price.) I'll go out on a limb and say we shouldn't have any issues with the 4-5 hour waits, but I don't know about the shorter ones. Domestic I wouldn't worry, but really have minimal international experience.

Anything leap out as "do not do this" or anything else I need to worry about, should know, etc? Are the shorter layovers viable? MUS or DUS?

Thanks - and with any luck, I'll get to the point where I can answer a question instead of asking....