I think leaving your Little one is a personal choice. I couldn't leave my Son now 8-months for more than a few hours with someone.... That decision is down to how comfortable you feel.
If your baby has never taken a bottle you may have to do a trial run with a little, as some Mothers have difficulty introuducing a bottle after so long of exc' breastfeeding.
I suggest perhaps you start pumping alittle each day and freeze it to build up enough for your little one. Then you can have more than enough for the time your Mum has him.
Do you have an expresser? If not you could drop in to a local BF centre and see if they will loan you one.
ABit of Reading for you to do....
"Ethanol - the chemical name for alcohol - is approved by the American Academy of Pediatricians for use during lactation.
Hale (Dr Thoms Hale in Medications and Mothers Milk, international research based textbook) found that a mother needs to have a blood level of 300 mg alcohol per decilitre of blood before her infant shows significant side effects (mainly sedation).
The legal drink driving limit in the UK is 80mg of alcohol per 100ml of blood.
100ml is a decilitre so this means you would have to have consumed between 3 and 4 times the legal limit for driving before the alcohol you were drinking had significant effects on your baby….and actually feeding at the time you were affected, too.
Alcohol reaches the breastmilk shortly after it reaches the bloodstream - so fairly quickly, but in dilute quantities. Hale says ‘the absolute amount transferred into milk is low’. It is estimated less than 2% of the alcohol consumed by the mother reaches her milk.
You can be sure your breastmilk is clear of alcohol when your bloodstream is clear of it, and the usual guide for this is that the body processes alcohol at a rate of one and a half to two hours per unit. Alcohol peaks in milk approximately 1/2-1 hour after drinking although of course this varies considerably from person to person (see below)
Hale does not imply it’s a good idea to drink whilst breastfeeding….he suggests waiting 2-3 hours after drinking, although I think perhaps it is difficult to pin down an exact time as this will vary in each situation.
Factors that should be taken into consideration include; the amount of alcohol consumed ie smaller amounts will leave the blood stream much more quicky plus the weight and age of the baby (this information is directed at healthy fullterm babies) A newborn has a very immature liver, so minute amounts of alcohol would be more of a burden. Up until around 3 months of age, infants detoxify alcohol at around half the rate of an adult. An older baby or toddler can metabolize the alcohol more quickly.
Of course how quickly each mum metabolises alcohol will also vary slightly depending upon how much food was eaten in the same time period, mums body weight and percentage of body fat, etc..so this could explain the more conservative time frame presented by Hale.
There is no need to pump & dump milk after drinking alcohol, other than for your own comfort, pumping & dumping does not speed the elimination of alcohol from the milk.
The La Leche League’s BREASTFEEDING ANSWER BOOK (pp. 509-510) says,
“Occasional or light drinking of alcoholic beverages has not been found to be harmful to the breastfeeding baby. Moderate-to-heavy regular alcohol consumption by the breastfeeding mother may interfere with the let-down, or milk-ejection reflex, inhibit milk intake, affect infant motor development, slow weight gain, and cause other side effects in the baby.
"
