I find that babies will often go on hunger strike in this sort of situation. So even with expressing, you may find that DS refuses to take a bottle from DH. If DS does take the bottle he may only have 1 to 2oz.
So on the day itself, I would suggest:
Feed DS as per usual. When close to leaving home, feed him again - top him up.
Be prepared to feed DS immediately upon your return home.
Having DH bring DS to you at work, I wouldn't bother. It's hassle for you, for DH and confusing for DS. If DS is to be able to take a bottle from someone else at times (can be handy if you and DH want an evening out and you leave DS with a babysitter), then you need DS to realise that the bottle is the only thing on offer.
So that DH has a supply of EBF to use for a bottle, build up a supply over about 2 weeks prior to the event. Find a time that suits you to express, a time when you are not stressed and say about midway between DS's usual feed times. You won't express much but by getting into a routine it should stimulate more milk to be produced for that time. DH can also start to try doing some feeds, by giving a bottle with say 1oz of EBF in it (or however much was in one of the early frozen expressed pouchs - remember to date them) with you then giving a BF as per usual immediately afterwards. A good time might be in the early evening, when you might want a rest and DH is around and able to have some cuddle time with DS.
After the event, DS could have a feed at the time you would have pumped, or you could do nothing, or if you feel the need to release milk, then pump off a bit and freeze it, thus building up a supply for when you leave DS with DH or someone else.
Take the pump to the event, so that you can relieve any pressure you feel in the breasts. Dump the milk, it's probably far easier than finding some way to keep it in a cool place. As DS will be wanting a feed immediately upon your return, you only need to relieve pressure rather than pump lots off.
Above is based on my experience as a childcarer who has to give babies a bottle and on what mothers have told me of their experience pumping.
Often a baby will take a whole bottle regardless of amount so don't worry about limiting feeds.
As a childcarer, that is not my experience. Babies can be very fussy and will take time to adjust to sucking from a bottle, plus whomever is preparing the bottle will take time to get the temperature right for how that particular baby will tolerate the bottle. The baby I currently care for certainly would refuse to take the entire bottle and even now at 5 months old, she still has times when she won't take a whole bottle.