Being the mum of two year old twins myself the biggest shock to the system and most difficult thing to cope with for me was the lack of sleep. Neither of my girls ever slept at the same time and it was hectic to say the least. If anyone would have offered to watch one while I and the other had a sleep it would have been a godsend.
Also something that i have done for a friend is go and visit and while there do some washing up or clean the bathroom or something. They may tell you not to worry, but insist and they will certainly appreciate it