I just got my first wedding cupcake request with a guest list of 150-175. I've given a quote for cupcakes and for the 6" cake they are requesting.
The wedding is only about 20 miles away. What do I charge for set up/delivery?
Also, I've told them I don't have a cupcake stand large or fancy enough for a wedding. Is that the job of the wedding planner(who is my best friend) to find one or is that my responsibility?

Well...
You will get 100 different answers for the delivery/set up fee that people charge. For my business I charge $2/mile one way with a minimun of $30. I found that when I charged $1/mile round trip people didn't like that I charged them to drive home. So, now I say "2/mile one way, I don't charge round trip" and they think they are getting a deal.

It is not common here to charge a set up fee. As a result, I never charge one - even for cupcake weddings. The largest cupcake wedding I have done was 288 cupcakes. It took me about 35 minutes to set it up, which is not long at all. Plus, when I tell clients "I never charge a set up fee", it again, sounds like they are getting a deal for their order.

I had a 5 tier wood stand that spins (build on a lazy susan) custom built for me. You can see the stand in my pictures. It cost about $475 (I can't remember exactly). Now, that is pricey but I rent the stand for $40 for my clients and it has more than paid for itself. The top 3 tiers are connected and the bottom 2 tiers are connected. They fit together by these little pegs. This way I can use the stand for both large and small events. All events are charged $40 to use it, whether they use half or the entire stand.

I would consider it the responsibility of the baker to provide the cupcake stand. You can purchase inexpensive ones online, but if you plan to sell your product on a regular basis, I would look into buying a nice display stand. As you post pictures online for future clients to see, having a nice stand goes a long way for the "eye candy" they want too.

Remember to charge a good deposit for the cupcake stand--that is, a separate deposit from the one for the cakes.

Figure out if you want to pick it up yourself to guarantee that you get it back. That might up your delivery charge per mile.

The bakery I worked for charged a $50 local delivery fee that included set up.

As far as the stand is concerned, I think it's up to whoever wants to do it. If the wedding planner has a certain look in mind, she may want to use a particular design and if she can procure it, then she should be the one to get it and charge accordingly. If you are the one to get it, you don't have to buy it. You can rent one from a party rental and also charge accordingly...making sure you have given instructions to either someone in the bridal party, the wedding planner, or the venue on how it is to be returned to you.

I charge a $25 deliver/set up fee for a 15 mile radius

a $50 delivery/set up fee for a 60 mile radius

a $75 delivery/setup for over 60 miles

and I always at least ASK if the customer has a stand that they want to use or ideas of how to display. But I also have a few on hand in case they want to rent one from me. I charge a deposit (enough to cover the cost of one) that they get back if they return it.