M.C.
Whew! Good luck with this. Well - yes - I guess I think you are maybe making a big deal out of a small thing. I personally never saw a problem with an elementary school age child missing a week or two of school - if she/he is doing well in school! Find out what the school thinks about it. This will back you up if they agree with you. If they agree with the ex- then, well - take the expert's (the school's) advice - and lighten up. Put the responsibility on the ex- and your daughter to get the work done...generally the easiest time we found to get our kids to do their school work while traveling was - in the car and/or on the plane. Get it over with before the visit to family ever begins! Can you make that happen? No. You can say the school suggested it and it can be our little secret. I would NOT stay up late the night before she returns to school to make the ex- and your daughter look good. The message your daughter gets from that cannot be good. (Daddy is a screw-up! Look what he did!) Unless you have a supremely better temper than I do, it would be better for your daughter to face the consequences at school of not having the work done on time than for the two of you to have had the type of experience I am imagining must have happened. You don't need to scold. You just check and then give your daughter advice on letting the teacher know that it didn't get done and ask for a new deadline for completing it.
If the school agrees with you (they might - it has been many years since my kids were in school)...better check with your divorce decree before beginning world war 3...does it spell out how and when visits should occur? does it specifically provide for this type of event? if so, don't overstep your legal bounds before beginning the war...then - I have no idea what to say. Me and my ex never amicably settled anything after our divorce - so - clearly I have no advice worth listening to in this eventuality.