Can I handle a big group booking, like a wedding party all travelling together, on my portal?

Partly, but not usually as one single booking. Airlines set a limit on how many travellers can sit on one booking made through the normal search and book channels that your portal uses, and that limit is quite small. Above it, the airline wants the request to go to its group desk, where fares are quoted by hand, held for a while and often need a deposit. That process is not something a live search can do, so your portal will not quote a true group fare for a large party.

What you can do is split the party across several bookings. Your portal will let you do that, and most agencies handle weddings and family parties this way. The honest warning is that each booking is priced on its own, so the last few travellers may end up on a dearer fare if the cheap seats run out while you are working, and seats together are not guaranteed. Booking the largest group first and working quickly helps.

Hotels are easier. If the property has enough rooms loaded by the supplier, you can book several rooms at once, and you can repeat the booking if you need more. Very large room blocks, the kind where you want a held allocation and payment later, still need a direct contract with the hotel rather than a live supplier rate.

For a wedding party, the practical route is to get a quote from the airline group desk or your consolidator, then record that group as an offline booking in the software so the invoice, the passenger names and the payments all sit beside your online bookings. Check with each of your suppliers what their own group rules are before you promise the client a price.