check them ONCE every day, quickly, just open up and make sure all development is fine...most parents wont abandon the nest unless theres alot of stress.
however dont start touchign the babies untill there at least 2 weeks old.
teils tame down very quickly so as long as the parents are doing a good job i wouldnt pul for full hand fee ding untill 14 days...if you want to co-parent (allow the parents to raise but you do the occasional hand feeding id wait untill 3 weeks)
obviously this will be your first time hand feeding chicks...
some things to keep in mind
Brooder temperature if pulling the chicks completly needs to be spot on (theres lots of info online), make sure the floor of the brooder has something "none slip" ive personally used none skip shelf liners with shredded paper ontop. (like with baby chickens, newspaper alone or a glass bottom can result in splayed legs
i like aquariums for smaller birds and clear rubbermaid totes for larger birds
formular MUST be the right temperature, crop burn is terrible and it its too cold it wont digest and youll get a sour crop.
i ALWAYS feed right to left (syringe on the right side of the chicks beak pointed at about a 45 degree angle to the left side/back of the throat. NEVER aim the syrnge at the back of the beak as formular can get into the trechea and the bird can drown. always come in form the side of the beak.
good link for teil breeding/hand feeding
http://www.cockatielcottage.net/breeding2.html
i also practice (and suggest everyone does) something called abundance weaning...
it takes a little longer BUT youll end up ith much happier, healthy and well rounded birds by the time they go to their ne families...
the "Normal" method of weaning is at the time normally assumed best for weaning the hand feeder leaves food with the babies and stops feeding certain meals...exxentially forcing the babies to pick at the food even if there not mentally ready because they are hungry.
with abundance weaning however you still offer pick at foods (millet, small pellets, ect) (at about 4 weeks) BUT you continue with your regular feeding schedual...you simply let the babies dictate when theyve had enough/when to cut back feedings...
my macaw for example decided he didnt need his afternoon feedings and let me know by literally refusing the syrnge for his afternoon feedings, he still took his morning feed and his bedtime feed but at lunch time he wasnt interested...over the next few weeks he started eating less and less formular for breakfast untill one morning he refused breakfast all toghether...
in this method if the bird refuses a feeding at a meal time, you would still offer that meal for a few days after the initial refusal...jack for example refused his breakfast some mornings at first but would take a full breakfast feeding on other days...when he whent a whole 7 days refusing all morning feedings i stopped offering.
the idea being this method is a more natural way of weaning baby birds, it allows each one to develop at its own pace and increases their confidence to try new things. ive used both methods in the past and since finding the abundance weaning method i will NEVER force wean a bird again...the difference in personalities between forced and abundance weaned parrots is just incredible.
good luck on your new babies, teils especially grow so fast, theyll look like real teils in no time so enjoy every moment.
its very cool to see them develop every day!