For a relocation package at $30k, OP is definitely middle management, not an entry level developer. Have had a similar package and like I said, it worked out to a ~$10k loss. No regrets, was happy to eat the cost for what I got out of it.
Moving a family IS NOT the same as moving an individual. Whole different kettle of fish. I see folks saying that there is a sense of entitlement - that is an opinion.
Here is what I can think off right off the top of my head.
+ visas: $1000 TN/TD + accompanying visas ie spouse + child; 3x$160 for application, 3x~$100 to issue, total of app. $1000
+ legal & other fees $2000 medicals, paperwork for immigration especially for spousal / child visas etc (medicals for example, are $300-500 a piece!)
+ airfares: $3000 (go return - cheaper than 1 way + you set up your first visit back home), app. $1000 each, $3000 total
+ moving: $5000-$10000 $5k, you pack, someone ships; $10k - full service. Full service is way way better.
+ vehicle move $2000 assuming two cars, about $1000 each
+ storage $1500 Plan of taking out a storage unit for stuff you do not want to bring but do not want to dispose of yet
+ insurance $1000 move + storage + personal after you quit but before you start work at the new place
+ 2 months rent/hotel $5000 Assuming 2 bedroom minimum; this is not your final home, this is where you stay while you find a home. For SF, this is LOW!!!
+ real estate $3000 a broker to find a home (neighbourhoods, schools etc), you can do it without an agent but your work / life will suffer
broker
+ career services (spouse) $2000 get your spouse into the workforce
+ house selling costs $5000 small repairs, painting etc: you get this back when you sell but you need it upfront
+ first 60 days $3000 For day 0 to day 4/5-ish, you are bleeding cash, buying everything! Toothbrushes, meals, meds, plan on at least 30 days before life stabilizes then big money on taxis/car to see houses + schools etc
living costs , appropriate clothing
Re: taxes - for Canada, you do not reduce income amounts to reflect taxes paid, CRA offers a credit but full income must be reported.
Some Canada -> elsewhere specific gotchas that you need to think about. These caught me the first time, wish I had known.
-> exchange rates: get your package in the currency of the country you are going to, not Canadian. $30k canadian is a 40% discount on US and you will be buying services in US
-> metro homes are much smaller than the typical canadian home even in the GTA, unless you are in a condo. Stuff from your 3000 sq. ft. home will not fit in the 1500 sq. ft home you will end up in. For example, dont bother with a king size bed. Or a large couch. They won't fit and will end up on the street.
-> with kids, first find the school then find the house. Not the other way around. Schools have waiting lists, make sure you talk to them and make sure they will admit your child before you start looking for a home.
-> for houses, try to visit when kids would be home so that you can understand if your kids will be make friends. When we were searching, one place had a grass courtyard surrounded by houses, off the street, with more than 10 kids out - bikes, tennis rackets. We knew we were taking the house even before we saw the inside.
-> Proximity to transit, especially what you will take to work, is everything in a metro area.
-> if you are going to a metro area, bring your bikes, not so much the car. Or maybe one car. The one that can do more.
-> one benefit of full serve service move is they hold your stuff for up to 60 days while you find a house. If you move yourself, you have to put things in storage then get the out later then move then into new house. So, you essentially move house 3 times in 60 days. And where you are going, you have no friends. Just you and the spouse. I suggest that this may be bad for your marriage.
Drop me an email if you want more info shnm at 8t4t dot net