NO Problem, You can Apply for SIN at a later date, but you have to visit Hrdc office when you need to apply for SIN Card, I hope you are not immidiatly going to work in Canada, SIN is needed for work and taxes.
When you land have Goods to Follow list with you(2 Copies)
Keep 2 Passport Size phothographs with white background with you, they can use it for your PR card, do not forget to provide your Canada address( it can be your Friend, Relative Address, inform them you will be on this address, so that you can get your PR card on this address by mail, if you do not give that address, then you have apply for PR card from Canada and have to collect PR card with in Canada, better apply at the time of landing and your relative or friend can recieve it in your adsence and if you wish he will mail it to you.
Take the recent Bank statements of last 2 months., Passport,Landing Document.
Do not forget to post your Landing EXP and Coming back to US in detail, it will help others.
Good Luck!!!