We have a BRIG 380H with 50HP Merc. Be careful NOT to get into too large an inflatable UNLESS of course you're looking simply to buy another boat. "IF" your interest is truly in a tender and your focus is on your 6' 280# Son-In-Law, I'd personally recommend the slightly larger 495cm EAGLE-5 w/115HP. Ours at 380cm is marketed as a 5-Passenger and it's really comfortable for 3-persons. Same practicality applies to the EAGLE-5 which says it's USCG legal for 7-Passengers albeit I assure you is most comfortable for 5-people, including your Son-In-Law's profile. Here's a link to BRIG: http://brigboats.com/models/eagle/eagle5/
Lastly, seriously look into getting a JET DOCK for your BRIG when at your Cruiser's berth; you'll protect and use your rather expensive new nautical toy considerably more, GUARANTEED!!! www.jetdock.com
Specific JET DOCK for tenders: https://www.jetdock.com/products/univ-14ft-boat-dock.asp