This is not really related, but i do this, and don't expect children from rough beginnings to want to do family activities with you. You may get told to fuck off, and they just do their own thing.
So, i guess, find out about the children first and don't have expectations about them cos that just sets you up for hurt and disappointment ☺

Making play doh at home, colouring in and crafts and going to the park to kick a ball and being pushed on the swing is more important than paid activities.
When you head out pack food and buy treats.

For paid activities plan ahead where you are going to budget, there’s no need to do lavish things, planning too much could overwhelm them.

Remember the kids have probably been raised on nuggets, 2 minute noodles and Maccas, giving them the choice of what they eat for their first dinner can be a comfort for them, after that cook the same meals for everyone in the house.

I think it depends where you live too, I would assume prices are higher in Syd / Melb than regional activities. You could always bring food and drinks as well if budget is an issue. When we go to zoo etc we bring a picnic, the kids dont mind we let them pick what food drinks to get from Woolies but thats the only way we can afford to go with 3 kids and both being on reduced hours.

Look up the activities you want to do d as HD check the price for a family of 4. Lunch at the bakery will just be double what you pay now

I'd say budgeting about $100 a person would be enough for an activity plus a decent meal out. Often you'd have money left over but allowing that much would give you a fun outing , a nice meal and probably also an ice cream and a drink/ snack.
I have 4 young kids so weekends out get expensive (I'm not spending $100 a person because my kids are all under 10 still, but judging by costs of young kids teenagers would be that little bit more expensive)

Teens are expensive. It’s not $100 more like $100 each so x4 = $400
Having said hiking, beach, sport are relatively free/cheap.
They might have issues so time together will be more important than money spent. Family bbq, PlayStation multi-player games, backyard games are cheap activities.

$200 for the week is plenty. Family passes to places like the zoo, art galleries, museums are worthwhile investments. Scouts is cheap and teaches a lot of skills. Camping is low cost. Can do it in the back yard. Offer to pay for music lessons. My kids both learned guitar.

Maybe consider engaging them in some kind of sport where they will develop self esteem, learn social skills and the value of teamwork. Then ypu can go out as a family after the game etc and not have to spend a lot... maybe just an ice cream or something on the way home.

Really depends on the activity. Entry fees to different attractions can range from about $20pp to $80pp and then depends if you buy food or byo. As a rough guide I’d budget $100-$150 per days activity. Some weeks will come in well under if you just to a park/beach etc then the money can roll over to the next week when you might do something more lavish and splurge. Reassess once you get to know the kids and figure out what types of activities they enjoy doing.

Best to plan for $100 per person for activity n food

It depends what you are doing. $80 min to $300 easily depending on the activity.

How old are the kids? Do you have any info on their background? You should join some support/Facebook group with other foster parents as they will be able to help you with a lot of foster-specific/common situations. If you've never had kids before then yes this is going to be a big jump into the deep end!

When my family of four gets takeaway (2 adults, a 3 year old, a 5 year old) it usually costs about $40 (Brisbane, Queensland, Australia), whether that's lunch or dinner it always ends up being about $40.

I don't think you need to do paid activities now. Do things where the kids can learn that it's ok to have fun, and that you're not pressuring them, and you're not pretending to be their new parents and play happily families. Again, some advice from people who have been doing this for a few years is really going to benefit you. Maybe a playground so the kids can just get out and have some fun in the sun, bring some morning tea to share together then let them play if that's what they want, or you can push them on the swings if they want.

But please find a community of foster parents because you're in for some great but also hard times, and you need experience and wisdom from those who've been doing this for longer :)

Best of luck to you!

If you have the money when you first get them within the first week take them shopping for some new clothes even maybe a little toy/stuffed animal - talking from experience with foster kids.