This is a question that I have been struggling with most of my adult life since we've always lived in "cool" places like California and Colorado! I have had guests come and stay for a week, let me feed and chauffeur them all around town without even a thank you note. I have had other guests who are super respectful and may eat some meals with us, but either offset it with a gift card or taking us out to dinner. And, oftentimes the best, is when my cousins (in college so I knew they had no money)helped a ton with the kids, and one night cooked me dinner! So, any extra money I spent on them had been so worth it! So, the point is that there really is no magic formula for expectations when you are hosting guests. But here are maybe some thoughts that make sense to me:
1. I base my expectations on the age of my guests. If they are older, like my aunt and uncles, or people that I am not super close to, then I expect that they will at least take us out to dinner or chip in for some things. If guests are either friends my age or younger, like my cousins, I usually foot the bill for most things without much expectation. As my cousins get older, I now find them wanting us to come stay with them and I'm sure they will be wonderful hosts to us!
2. I think it is kinda a rule that you provide guests with food in your home, whoever they are. I usually just try to have things on hand for breakfast at least, maybe a few things for lunch. Nothing that takes you a lot of time. Good things are fruit, muffins, cereal, lunchmeat. You could even leave it down in the kitchenette if you want. Dinner is the hard meal. I found it easier to go out as then the guests could not possibly expect you to pay for them and they should actually pay for you at least once. But, I know that gets pricey. So, for a week maybe think of two or three dinners that pretty inexpensive to make in bulk- like soup or spaghetti. They key is to keep things very simple, and you may find that you don't spend too much more than an average week on groceries.
3. I think having people expect to have you drive them everywhere is ridiculous. Offer to take them to the light rail station or bus stop. People should be considerate of the fact that you have three kids, and use them as excuses to not haul people around town whenever possible (like, "it's Johnny's naptime so I just can't take you to "blank")
4. Do not knock yourself out! It seems like the more you provide, the more is expected. Just be clear about your lifestyle and habits, not mentioning anything about the money aspect (meaning: not mentioning that you may be changing your lifestyle for the week they are there to not overspend). For example, just say "hey, we're pretty laid back around here. Help yourself to muffins for breakfast and a sandwich for lunch, but I don't cook much anymore. Do you want to catch dinner out a few nights?" If I cook, then I say we eat by five, so if guests are going to be back later than that I tell them to catch something on their own. I reality, we eat closer to 7, but with guests sightseeing, being back by 5 is hard, so I usually avoid having to make a few dinners! Encourage day trips!
5. One advantage of being a host is that you are in control of the situation. Be gracious when they are in your home and things are going appropriately, and be a little snippy when guests overstep. Decide that you are going to relax and have a good time and not worry about money for the basic things so that your guests feel welcome. But, for example, if your guests arrive at your home at 7pm and haven't had dinner, I'd make it clear that they either should have eaten with you earlier or gotten their own dinner out. It's all about boundaries as you are the host, not the maid. This, for some reason, is easier for my younger guests than older guests! Go figure!
So sorry to write you so much. The thing is that if these people may come to stay with you again in the future, you need to set up the boundaries or else you will run yourself ragged. Anyone with tact knows how hard it is to host as well as take care of 3 kids! But, on the other hand, people who are not willing to rent a car may also be looking for a cheap vacation! So, create the balance yourself! good luck! And, if guests come and do not do anthing to off-set the cost of having you (even with something small like a bottle of wine, watching the kids for a night, whatever) then I would not have them back.