Three non-sleeping children and I'M GOING TO A HOTEL THIS WEEKEND

[TerriblyPoshAccent]

Unfortunately it does coincide with my sister's wedding. How early do you think I can sneak off for a lie-down?

Go during the vows whilst everyone is distracted.

That bit after the ceremony and before the meal when people are mingling and taking ages to do nothing much - top nap time, I'd say!

Could you not arrive, get 'sick' and spend two days in bed?

Get someone to Skype the wedding.