Julie,
the only caveat I'll mention is for you not to under-value your work. Handlers love to charge $75 to wave liver in front of a dog for 10 minutes but don't feel that what we do as photographers or ad designers is worth what we charge.

So just make sure that you charge them a fair price for both the photography and the ad design and keep a tally of it against the handling fees. Sending each other invoices and canceling out the charges in trade is one way to keep track so nobody feels they've been robbed.

When we trade, there's a tendency to keep it very informal because "everybody knows the deal". But at some point, somebody forgets how much work you did. So my only advice is to keep it professional and document everything.

When will the ad run?

Jim