Don't think present giving should be compulsory! If friends and family are truly understanding then a simple and honest explanation would be sufficient.
Alternatively,the spirit of giving dosen't have to be only represented by material gifts.If you are struggling financially,then why not offer gifts that cost nothing? Maybe offer relatives with children a night of babysitting for example,or to cook for them one Sunday,offer to paint a room next time they decorate etc? Offspring could offer to do all household chores one day in the new year maybe.If you happen to be creative then use your skills and make something to give.
These gifts will be appreciated and cost nothing,whilst retaining the true spirit of giving :)