If you are staying with family that can make it harder to carve out time because the relatives you stay with may feel entitled. On the other hand, I am assuming that both sets of grandparents, anuties and uncles, etc. honestly do want to see you and your children, even if your husband is 'awkward' with his own family. Here's what I would do:
1)Set up your own schedule ahead of time and BE FIRM and stick to it. It would be best if you can stay somewhere else entirely- at a motel or even a beach cabin of your own!- or with friends, but even if you need to stay with family for financial reasons, make your own schedule.
2) Email both sides of the family in advance and set up specific activities with them. Do the two families get along? If so, suggest at least one big family cookout or potluck dinner. That way the maximum amount of relatives can visit with you all at once at one event. Your kids get to see everyone and play with their cousins- it's a win! Of course, if your families don't get on, that isn't going to work.
3) Plan out visits or activities with friends ahead of time and be sure to let your families KNOW. Tell them " Oh, we won't be here for dinner because we're going over to Susie and her husband's that night." If they complain, etc. just gently remind them that your old friends are also really looking forward to seeing you and that you have already made plans, etc. Be nice about it, but don't allow them to guilt you.
4) Not sure what the issue is with your husband and his parents. But if he is that uncomfortable, then why don't you rent your OWN cabin for a few days AFTER you visit his parents? Again, if anyone else has an issue with this, just say very gently but firmly that the arrangements have already been made and that your husband has been working so hard and he just needs some one-on-one time with you and the kids.
People are always going to find ways to complain about things or get their feelings hurt. If you have been polite and reasonable and have not taken advantage of their hospitality, you should not allow them to 'guilt' you.
If they are hurt that you are going to see your friends or going to the lake without them, just be polite and say " I'm really sorry you feel that way. We absolutely don't want to hurt your feelings, but we just need some time for just us and the kids right now."
Good luck- plan ahead and stick to your plans! Be polite and grateful, but don't let family guilt you!